MacBook Wireless slow and unreliable

Well, It's not a home network. I don't have the ability to change the configuration on the Access point, (It's an enterprise-class cisco access point) and even if I did, we have 500 Access points across campus, and I certainly can't do that with all of them, for every other MacBook that comes in. I have rebooted it several times. It worked briefly before the software updates and than stopped again after I rebooted Thanks for the response though. Maybe I just got a lemon? Doesn't make me feel to good about recommending this machine to incoming students though :/

The settings on our routers are
A: Not under my control, and even if they were, we're not going to flash settings on hundreds of access points to allow MacBooks to connect. We have no problems with any of our PowerPC macs, although we have seem some weirdness with MacBook pros, which have been fixed by creating a location (which I have done several time)

B: Not causing persistent problems with ANY other machines. (including our intel iMac which has been connecting to the wireless network solidly since we got it) The Windows machines that exhibit this problem are generally fixed after re-adding our wep key to the preferred networks list. (which I have done on the MacBook, repeatedly) I have not installed boot camp on this machine to see if it exhibits the same behavior under Windows.

C: I can connect the MacBook to an unsecured wireless network that we run for guests which does not permit access to any of our network resources. I had it connecting to our secured network briefly yesterday afternoon, by selecting "other..." from the wireless menu in Internet Connect, entering the password and saving it in the keychain. I then put the machine to sleep. When I came in this morning and woke it up it said "None of your trusted networks can be found would you like to join network "network that I joined yesterday afternoon" I said no, because it was already in the trusted networks list, put it to sleep, woke it up again, same thing. If I connect to the network when it shows up in the list, it does not ask me for a password, says it has connected, and gets a 169.x.x.x address. Refreshing DHCP lease does nothing, and I suspect that it is not really connected at all.

D: I am suspecting this is a software/driver issue with the network card in the MacBook, or I got a bad unit. If it is software, I really hope it is fixed soon, as I simply cannot recommend this machine to students if it cannot connect to our secured wireless network. I would like to offer them something that is less than 2000 bucks right off the bat. It does not seem to correctly recognize that the network has a password, as such does not prompt for one. It gives feedback that it is connected, but it does not get an IP address. This has happened in other areas of campus, so it is not the wireless access point around my office. I'll probably call Apple Support this afternoon and see if they can give us any suggestions.

Thanks.

I did work with Apple Support. It is definitely a driver issue. Boot Camp identifies the card used in the macbook as an Atheros card, and the card used in the intel iMac as a broadcom (which does work). My immediate problem is solved, as the network admin was planning some changes, and when we tested his changes, it seemed to solve the macbook issue. (We had an unsecured network that was not broadcasting the ssid, and a secured network that was, now they are both broadcasting, and for some reason that solves the problem)
I think it comes down to it being a weird cisco thing, but it does kind of worry me that none of our other macs, including our intel iMac had this problem, and whether or not this problem will continue in the future. Glad to see I'm not the only one running into weirdness.