I think I found the problem.
I was mining with my CPU's and I found when I mine the pool's coinminer.net:18321/static/ or next.afraid.org:8117/static/ my wallet will fail after a couple of hours or so. I get the error (Not Responding) so as a test, I tested the CPU mining on coinminer, next and VirCurPool and I found that I don't get the error when mining on VirCurPool.
No idea why it happens, maybe someone else can test mine with their CPU's on the three pool's to see if they get the same error.