I've never heard of anything like that. Can you provide anymore information? Were you using a local user to login or an Open Directory or Active Directory user? Do you use a 3rd party program to tie into AD?
Do you have things scheduled to you Macs maybe via query so as they get agents installed they get scheduled tasks processing that could be slowing down or machine or interfering with logon depending on what the task(s) are doing?
Does the machine function normally after installing the agent until the machine is rebooted or the user logs off?
I do have ADmitMac loaded on the machine so it can be added to Active Directory and fully integrated. However it hangs regardless if using a local account or a Active Directory one. I don't think there are any scheduled tasks via query as it's a pretty lean / new LANDesk installation.
The machine seems to function fine until logoff/restart. However even without being able to logon I could remote control and even push a package to it. It's like the machine is fine except for the logon hang.