If you receive an error concerning the loading of your profile and Event ID 1000 - Source: Userenv appears in the Application Event Log, chances are:
1. You changed Permissions on the local %system root%\Profiles folder. The EVERYONE group needs Change permissions to load the profile. You also need at least Read on the system root and drive root.
2. If the system partition is low on space, or the registry size limit has been exceeded, the profile can fail to load.
3. The profile is corrupted. Either the local Ntuser.dat, Ntuser.man or the roaming copy of Ntuser.dat is corrupted. When this occurs, there is usually an event indicating a RegLoadKey failure. (not in this case)
4. The %system root%\Profiles\Default User folder is missing and the account does NOT have a cached local profile and is NOT configured for a roaming profile.
When you look at the Application Event Log, Event ID 1000 will have one of the following details where %s is the UserName and %d is the system error: