That disclaimer is on many HDTV sets ... I think it's primarily so they don't have to answer any support issues related to PC's. MANY of the HDTV's work much better with a DVI input than with their VGA inputs => very frustrating. I helped a friend set up a 60" Sony A2000 for use with an HTPC ==> and although it's a great TV, its VGA input is lousy. But it works great through the HDMI input (using a DVI -> HDMI cable).
... that said; yours should work fine with the VGA input, since it does so on other systems. This HAS to be a driver/compatibility issue => unfortunately it can be very difficult to find the exact right combination to make it work.