My wife is having a similar problem on her MacBook. It takes about 10 seconds for it to find and join our home wireless network. We are both experiencing EXTREMELY slow and laggy connections; we have Verizon FIOS and very fast connections over ethernet, but Airport seems to slow it down to a crawl.
I'm using a WPA2 personal network with MAC filtering, and don't have any problems with my Dell work computer, so I'm fairly sure it's a problem with the 10.5.4 Airport software.
The first thing to try is to delete your network from your list of known networks in the Network preference pane, close the preference pane, then reopen it and add it back.
There is a long-standing known bug regarding occasional failure to reassociate with a network after sleep, but most it's just that, occasional and not constant.
Also be sure your router is running the latest firmware revision available from its manufacturer.
I have 3 networks, @ Home with AirPort Extreme connected my MiniMac with my wife's MacBook 15" pentium,.. @ my work with Linksys Router connected 2 iMac- 1 G4 the other pentium 20" 2 months old & the old Cube G4 connected via ethernet, and the last network is in my travel Apartment, connected with my landlord network using a Netgear router.
These three networks, they were working very well before I did install OS 10.5.2 after this the connection between computers start dropping frequently, I been updated since then hopping that apple fix the bug. Trust me I even change one of the router because I thought was a hardware problem. I been a loyal Apple user since the Performa 600. Never have a serious problem like this before.
We had to have the Airport card replaced in one of our Pro's, the "N" enabler wouldn't work on it. After replacing it worked fine, then they came out with 10.5.3 and now all the Macbooks updated to it have Airport connectivity or performance problems.
Biggest problem noted so far, is the System Profiler/Logs/System.logs are full of "Airport Beacon (Lost)" errors, line after line.
The fix needs to come from Apple and its not included in 10.5.4 either, if you see those errors in your system.log, roll back to 10.5.2 and the problem goes away. I wished there was a way to restore 10.5.2's Airport configuration because Automator is much better in 10.5.3. But without Airport I have no net connection.
Check your system.log files for that Airport Beacon Lost error, if you have it so far the only fix I know of is rolling back to 10.5.2 with a Archive & Install, be sure to save your User and Account settings. Takes a couple hours but you don't loose anything, just annoying is all.
There sure are a lot of posts with the same Airport problems, you can try deleting your Aiport configuration, logging out and rebooting, but that is only short-lived and it doesn't resolve the problem.
Since rolling back to 10.5.2 my Airport connection and performance has been fine.
My macbook has the latest firmware updates installed, it is a late 2007 machine.
Please don't make the assumption that because that's what fixes connectivity in your situation, it's a general case fix.
Also remember that rolling back to 10.5.2 reopens several security holes that have been fixed in later releases as well as causes the reappearance of several bugs that have been fixed since 10.5.2.
I don't blame you at all for doing what you did, but be aware of its limitations as well.
Well, I would be out of warranty for two machines, so I'd rather not pay for the replacement (and be without our computers for several days) just to see if that's the problem. Basic troubleshooting methodology (testing the same hardware and same Airport network in Bootcamp) leads me to believe it's an OS X software issue. I've tried rolling back to 10.5.2 and had it work, and tried updating but with all 3rd party software removed, and had intermittent success. That's what's so frustrating - sometimes it works, sometimes it doesn't.
I just want to chime in here to say that I'm working on TWO networks (in two locations) that are entirely Apple Airport based (no Linksys, etc.) and this same thing is happening consistently since the 10.5.4 upgrade.
The primary symptoms seem to be that the machines (and I have multiple machines - all Leopard 10.5.4 MBPs) can't find the Airport network upon waking from sleep. Sometimes, they find the network but are challenged repeatedly for the password...and we enter the correct password to no avail. Then, once the machines are rebooted, all comes back as normal. Until it happens again (upon waking from sleep).
Also, there seems to be a possibly related problem that's visible in Mail...Mail seems to go offline (you get the little warning triangle with the ! in it next to the Inbox) repeatedly throughout the day. The airport status indicator in the menubar (OS) looks fine...all of the possible bars showing...but Mail goes offline until you ask it to "Get Mail"; and then the triangle goes away and Mail goes right out and checks mail (seemingly without a problem). But the next time you look at the Message Viewer, there it is again. This just goes on all day.
In short, I don't know if this is a connectivity problem (machines losing their connections with the network) or perhaps something else (keychain problems?)...but ALL of these have started with the 10.5.4 upgrade and it's happening on multiple machines on multiple networks.
Sorry guys, this is not a solution, just a little more data.
For what it's worth, I'm 100% Apple running an Air, two iMacs, a Mini, an Apple TV, two iPhones (old and 3G), two Extremes and 4 Expresses. Having upgraded the Air and two iMacs to 10.5.4 and the Extremes to 7.3.2, I cannot connect to the network for longer than a couple of minutes with the Air and one of the iMacs. The other iMac is completely fine, as is all the other equipment. I haven't upgraded the Mini. All other equipment is at its latest version.
I have now replaced the Extremes with a single brand new Extreme running 7.3.1 and have exactly the same problem, so it certainly doesn't look like it's the network. Today I took the Air into my local Apple Store and experienced the same symptoms, i.e. I could only connect to their network for a minute or two.
If anyone has any ideas, I'd love to hear them. In the meantime, I'm trying to get a slot with a so-called Genius to see if they can get my Air to talk to their network in the store. If I get a result, I'll let you know.
Please do let us know; I also assume you've tried the trick some have had success with with their Airs of shutting off Bluetooth.
I've tried to reproduce the sleep issue in Apple Stores by enabling Bluetooth and putting their machines to sleep but without any success (they always reconnect on waking no matter what I try.)
That in no way means there's not an issue here, and I'd really like to see what a Genius does with a machine that's obviously displaying the symptom in-store (aside from a reinstall; if that does fix the problem I'd like to know as well.)
If you are using a "N" wireless network, check it for yourself,
1. Utilities/System Profiler,
2. Software Logs,
3. open system.log, scroll all the way to the bottom,
Look for line after line of errors indicating:
date/timestamp computername Airport Beacon (Lost)
IF so THAT is your problem, removing and adding back your Airport card is a waste of time, 10.5.3 breaks it, roll back to 10.5.2 and you will see the above error disappear.