Hello, I've been getting this error in modded minecraft only this week and not before - it claim I don't have enough memory and crashes after having the world open anywhere from 0s-30s into playing, the memory part isn't true I have 14gigs allocated and it seems it thinks I don't even have 0.00016gigs allocated. Im not to techy when it comes to non traditional modding errors so I need some help interpreting!
First, NO version of MC needs 14G memory allocated. That could be your first problem. Second, how much RAM does the PC have? NEVER allocate more than half of the PC's RAM to MC. Modded MC should need about 6-8G to run properly.
Your Hard Drive might be getting full also. Windows needs space on the HD to write temp files as memory.
I would also check to see what other programs are running when you play MC. These can be competing for memory also.