VGA to USB?

Hey guys, I've had my plasma tv hooked up to my imac via the VGA port, but recently it has been failing me to the point where the only way it would work was to put a pen between the VGA and Ethernet port to make the contact. That worked for a while, now it only makes contact sometimes and when it does the color has an overall yellow tint to it . My question, have searched around and not found a definite answer, is there any way i could connect my plasma tv from its vga port to one of the USB ports or firewire ports or any other way to connect it to my iMac? I dont want to spend the money to fix it as i plan on upgrading sometime in the next few months. (right now it is a 2007 iMac 2.4 GHz intel core duo 800MHz Bus Speed w/ 4gb 667MHz DDR2 SDRAM) TIA

I'm guessing you're using the mini-dvi to VGA adapter cable.

Mini-dvi is the only way to get video out. You can try replacing the adapter but if that doesn't work I'd suggest the socket on your iMac is damaged (perhaps a dry joint etc)

I'm positive it is the socket, this is the third mini dvi vga adapter I've used and was wondering if there was an adapter that could connect through usb like this one Newegg.com - StarTech USB VGA External Dual or Multi Monitor Video Adapter - High Resolution USB2VGA2 USB to VGA Interface , but for Mac. Know how much it would be roughly to replace the socket?