Error Out of Memory

I keep running into this same error message java.lang.OutOfMemoryError: Direct buffer memory. I am running eclipse on windows xp. I have already increased my java heap size to -Xmx512m. What else is my problem. I am only loading a simple plane object and some particles. What else could be the issue? I have to be doing something stupidly wrong (probably with particles since my plane is such a simple object). I don't want to post a huge amount of code but if you guys need it I will. Thanks in advance.

It doesn't look like any of the mods are on so I think I will hit the hay but I am going to check this tomorrow so hopefully the mods will see this question by then. Thanks again to guys, you have been very helpful so far.

direct buffer memory is set like that: -XX:MaxDirectMemorySize=512m (whereas 512 is most propably too much)