Certainly check the RAM as was suggested. Around here, Virginia, RAM is still fairly cheap. I just picked up a 512MB chip for $30.

Unfortunately my machine will only support a gig.

You can also take a loog at the nvidia 6600 GT or the 6800 GT cards. Both are good. I just put a 6600 GT in my machine for $130 from newegg.com. Not yet sure if it will work with G3, but it should.