NAMD fails with Octahedron. AND Analyze trajectory fails

Hello, 
1)I am currently working on DS 2016. I ran a 2ns simulation consisting of 1000 frames using NAMD protocol. the simulation went just fine. when I analyze the trajectory for RMSD (main chain atoms), the protocol runs for about 5 hours then fails with this message : "GC overhead limit exceeded"  

2)I ran a different simulation with truncated octahedron solvation box, it runs perfectly using the standard dynamic cascade but fails directly using NAMD with the message PME nneds periodic boundry