PLEASE HELP!

Every now and then my miner will stop finding shares.  Why does this happen?  The green light will stay on for extended period of times and sometime the red light stays on.  I feel as though this is a driver issue.  The miner has work being sent to it but never finds/accepts any shares and my pool reports hash rate of 0.  If someone could help me this, I would be eternally grateful.  Thanks in advance.