How big is his profile? You mentioned having deleted his profile and this temporarily fixed the problem. Have you tried deleting his Internet Cache and temp files?
If you look at his profile, are his temporary internet files and Temp files being kept in:
C:\Documents and Settings\%username%\Local Settings\Temporary Internet Files
And
C:\Documents and Settings\%username%\Local Settings\Temp?
You can change the locations for the Temp file in the system properties-->Advanced tab, 'Environmental Variables' button. Just edit the locations for .TMP and .TEMP files to point to C:\Temp
For the Temp Internet Files, go to Internet properties-->General tab, 'Move Folder' button. Change the location to the root of the drive, it will automatically create the folder 'Temporary Internet Files'.
If you use roaming profiles and he logs into more than one machine, blow away his profile on all the other machines he logs into.
Hope this helps,
DF