Hi,
how's your pc connected to the TV - it sounds like the pc is outputting at a frequency or resolution not supported by the TV, in which case, maybe closing down, attaching a monitor as well (if possible), then playing with the settings until you get a stable picture, may work.
Tony
AMD64X2 6000+ | 3Gb Ram | 750Gb Maxtor SATA | 200Gb Samsung Spinpoint for Vista | ASUS M2N-SLI Deluxe | FloppyDTV + Dragon CAM | Pinnacle 7010ix | XFX 8600GT Silent Video Card | LG Blu-ray/HD DVD Drive | Xbox 360 | Arcsoft Total Theatre