Only 128? Damn man...
In Worldstone even with 512 it can drag down pretty bad because of spells flying around and such, it gets extremely choppy. For people who dont know, choppy is like running in slow motion, and while its choppy you can get dysynched easily. I hate to say this, but 3d mode isn't usable by anyone, and I do mean ANYONE. Even peeps with Geforce 4 Ti 4600 (4800?) with over 512 RAM gets skips on it, blizzard made that too... strong. Post your OS and processor speed. It also might be that your motherboard is overclocked, it puts a strain on your system, or so I've heard.