Freeze while applying changing

My desk top occastionally freezes in a seemingly random manner when I apply changes in LR or from plug-ins like Color Effects or Topaz filters.  I have waited for upto an hour hoping it was processing something but always end up having to hard reboot.  It usually takes place at the end of the process, when I reboot any changes have been applied.  Any guidance would be helpful, wondering if it is a hardware or software issue.