I don't normally do things like this, but I thought I'd share a tidbit of wisdom that I've acquired very recently.
Being a junior network administrator of a fully microsoft network means that I sometimes have to dig very deep for solutions for the odd problem that doesn't happen very often.
Today this problem was the configuration of a recently purchased laptop to replace a user's 5 year old and misbehaving lappy. After doing the standard stuff (joining the network, assigning proper admin permissions, installing firewall client and such), I tried logging on the user to configure everything... Only to get a one-minute long "Preparing Desktop..." and then getting the following message: "Your User Profile Was Not Loaded Correctly!" (This was in Vista, the error message is similar in XP and 2000)
After a few minutes of googling the problem I was no closer to a solution to my problem. All the results in the search were about deleting local profiles and registry keys related to the user profile... Which were of no help to me because the local profile never had the chance to even be created.
I finally identified that the issue wasn't on the computer at all when I tried to logon to her profile from another PC and had the same issue! So I started looking elsewhere... On the domain controller. Turns out that there was nonsensical data in the (believe it or not) "Profile path:" box in the Profile tab of the user's properties... And her home folder was misspelled. Honestly, I don't have any clue how that happened or how she was able to access her home folder's files in the first place. But now that this is fixed, everything is fine!
So I pass on this knowledge to the reader. If you ever get a "Your User Profile Was Not Loaded Correctly!" message, if the local profile isn't the issue, take a quick glance at your user's profile settings!