I might be able to give you a hand... I've worked with plesk before on several occasions, so I know it can be a pain sometimes. Could you give me more details on what the problem is? Do error messages come up? Blank pages returned to users? 500 or other server error messages? Also, what version of plesk are you running, and was plesk installed before the server was upgraded (and if it was, what version)?
You may contact me through e-mail if you don't want to discuss this through these forums @ joshb@npt.com.
-JoshB
