/vz/cp/psa/frameset was not found on this server

[mikeyv]

I am having an interesting issue with one client on our VPS server, where he gets the following error when trying to click the plesk control panel /vz/cp/psa/frameset was not found on this server.

No other accounts on this VPS are being effected by this issue, so I was wondering if someone could shed some light on what might causing it.