First of all lets go through this list...
a) get a grip on yourself
b) ARD is not as unstable as you make it out to be, in several months of use it crashed once here.
c) your example illustrates your inability to set up ARD properly
A+B i can't help you with. C, well if you read the documentation and how users and privileges work in ARD you won't encounter 'access denied' issues. In short there are two ways, local and directory users.
Local is the easiest to set up and if you're an administrator then I'd suggest you create a user on each machine with admin rights and then hide the user from the login screen. Having root access to clients are also preferable for sending unix commands.
Directory users/groups is far more complicated as you'll need proper understanding of OpenDirectory or ActiveDirectory for it to work as intended.
Much like you I gave a response that's not saying an awful lot so next time when you post... Explain something properly and detail what you try and achieve and also how you go about it. Maybe then you'll get a useful response from me or any other member here. Jumping in and just swearing and throwing words around gets nobody anywhere
Can you connect to it in any other way? Like file sharing or anything?! If you can't even connect then the problem is likely outside of ARD. Are you on the same network as this iMac? Or are you connecting over via internet? there a firewall between you and this iMac? if so you'll need TCP/UDP Port 3283 and 5900 to be routed to that machine if there is a firewall between your computer and the other iMac.
Just give as much relevant detail as possible.
i connect over the internet and have connected in the past to this machine and router. the mac firewall is off.
i have not been able to connect to this machine since 10.5.3
all the ports for ARD are selected and set in the router. is there a power PC incompatibility? are there alternative ways to connect like VPN? I can always connect through ichat and then ask to screen share but that requires the person to be at that computer and sometimes i need to work on that machine when no one is at the PPC.
I have found a suite called Casper from Jamf Software.
It is ARD on steroids and much much more.
More expensive than ARD and you'll need it's own box to run on.
It's a web front end and also GUI apps as well.. do a google search from Jamf Software.
You can get a 45 day full working demo after you sit through a web demo.
Best thing about that it integrates into Active Directory for user info. Which is very nice since I have 3 buildings in Europe to manage and one in LA.
Does packaging, network imaging, versioning, inventory.. quite a bit. I also like the software accounting/licensing
It's a really good IT tool. Best thing I like about it allows blacklisting.. no more people installing "apps they shouldn't".
And it does it all over ssh ... you must have that enabled firstly on the clients. Gonna have to read the manual there eh?
Gonna give it a go, since apparently I don't know how to use ARD properly. I got it going yesterday and have doled out the blacklister so far. I'm waiting for the first phone call... "Ummm... my LimeWire, BitTorrent, etc. isn't launching anymore." Mwuahahahaha!!!!
Casper is nice for deploying and stuff with the presets feature. Also useful for using it as a tool to boot off the network to reimage a machine that way.
But after that I have to say that it's just a huge pain in the ***. If I'm working on a group of computers that I have to install software on then I have to make sure those computers are on and on the network before I even start the Casper program. Otherwise it will return an error that it couldn't communicate with the machine.
Personally, other than the first two sentences pf what I said, I've found ARD more useful. Especially in that I can send mutli-line unix commands whereas in Casper you're limited to just one line.
There are a few things that I have done in the past for this.
The first thing I would try is resetting the password for that machine by double clicking the machine on your list.
If that doesn't work. I would physically go to that machine and reinstall the Remote Desktop client on that machine. I have seen that after that, it seems to work.
I think most people will find that there isn't one tool that is ideal and does everything. Currently I'm only using ARD, but have found that I am outgrowing it very quickly... it just doesn't have some of the functionality I really need. However, Casper Suite looks great, but again it doesn't do everything that ARD even does. So I think a lot of people will find themselves using more than one solution to be able to do what they need.
Radmind and puppet are also things to take a look at... both are open source. I haven't had much time to devote to looking at anything other than ARD lately.
As far as your ARD problem... check your client settings (maybe run install again). Sometimes you may need to remove a computer from the all computers list in ARD and then re-add it again. Sometimes I've had to click the properties of a computer in a list... re-enter the password... and it starts working again. If all else fails... lookup the kickstart commands for the ARD clients and play with that a bit.
Also if you are connecting to a machine through the internet or over a wan, make certain that the ip at the other end hasn't changed (the router/modem ip) unless you do have a static one provided by your isp.
We use ARD extensively and its awesome. Outside the network we use Team Viewer.. its equally awesome in that our end users, not always all that tech savvy, can use it via one simple click (oh, and assuming they can read...ha ha!) Check it out: