Which IP are you using?
It may be an issue of needing to clear your DNS cache.
Try flushing the DNS cache. To do this in XP, click Start > Run and type cmd and Press Enter. At the command prompt, type ipconfig /flushdns and press Enter.
Since the forum uses the same URL as on the shared server but has new dns settings on the VPS this resets them as I was told.
In Win 98 Start> MSDOS>command prompt