I resolved this problem by reducing the number of processor cores to something less than the host computer.
My host computer is using an i7 with 8 cores. So I was using my virtual machines with 8 cores when running them in Workstation 9. I eventually tested the problem machine on Player which required me to reduce the number of cores to 4 and had no problem. I went back to Workstation 9 and it continued to work (cores set to 4). BUT then I moved the setting back up to 8, the problem started to occur. I changed the number of cores to 6, only because there is not a 7, and I haven’t experienced the problem since.
Apparently by running the guest with the same number of cores as the host, a resource issue is occurring and the host cannot accommodate the processing needed by the guest.