I have 4 GB of ram, with 3.5 GB available to use. I don't know what the problem is, I can't play for more than 5 minutes without it messing up on me. I also get weird random spikes of no lag that i can play for 45 seconds.
Specs:
32-Bit OS, 32-Bit Java.
Nvidia 8600m GT
Dual-Core T8300 2.40 GHz
4 GB Ram