This happens with many different programs from the terminal. Usually accompanied with some error message about not being able to allocate memory.
When I try "free -m" this is the output:
martin@martin-ThinkPad-T410:~$ free -m
total used free shared buffers cached
Mem: 3823 3079 744 0 99 1159
-/+ buffers/cache: 1820 2003
Swap: 3953 60 3893
Why is my swap usage so low? Is this related?