Home Screen Resolution/Sizing Issue

A recurring issue with my Mac: upon waking from sleep mode, the top menu bar has either disappeared or stretched and the bottom bar has also gone of screen. I have to do a hard restart of the computer to fix it, but it's pretty constant. The pic shows the full left side of my screen when it happens.

Any suggestions or fixes?

 

Thank you for the reply. I'm running a 2.7ghz Intel iMac made mid 2011 I'm running OSX Lion. The graphics issue is something that's been on and off for a couple of years. It's generally not a big issue, but it may be getting worse.

I did a NVRAM reset. We'll see if that works. For some odd reason, the Apple diagnostics did not take. I'll try again. Not sure if the automatic graphics switching applies to an iMac.

 

Update: The NVRAM fix did not stick. Back to it's old tricks. Having issues running the Apple Hardware Test. It won't initiate at start-up. Will try resolving that issue tonight.