I ran into this one the other day, and the solution was so simple it threw my head for a spin. Thought I would share it on the blog in case any other Citrix techs run into the same thing!
Software: Microsoft Server 2003, Citrix Presentation Server 4.5
Problem: Admins are complaining that when they log into some Citrix servers via RDP, they are getting profile unable to load errors. The only account that can log in seems to be the domain admin account. Error: “The User Profile Service Failed the Logon” “User profile cannot be loaded”. This happened after a weekend, so our best guess is that some Microsoft patches or updates ran during that time?
Resolution: We first tried ruling out profile corruption by deleting the local profiles for these users, and trying to get them to recreate we continued getting the error. It made sense that administrators were the only ones getting the error in this environment, and the users were connecting fine because the users were all on roaming profiles. The administrators were apparently on local profiles, which depend on the default profile. Further examination of the server showed that its default profile was missing. When compared to a working server, we noticed that the default profile existed on the working server. We copied the default profile from a working server over to the non-working server, and it resolved the issue.
Note: If you are troubleshooting a similar issue and continue experiencing problems, I recommend you enable Microsoft USRENV Logging, and take a log of the attempted logon so you can try to see where things are breaking down: