iMac loses Internet connectivity upon waking from sleep.

I have a mid 2011 iMac and the issue I'm having is that the computer will lose connectivity with the Internet via ethernet connection after waking from sleep. It happens only periodically and it never happened before installing Mountain Lion. I am current running 10.8.2. The problem cropped up after upgrading to Mountain Lion but happens about one in 10 times. Called support several times and they weren't able to resolve it. One tech suggested deleting some network preference files (four in all). Another had me make a new location in network system preferences and that didn't work either. The only way to resolve the issue is to reboot the computer. It's a minor issue I suppose but annoying nonetheless. So, I was wondering if any other users were experiencing this problem or have a solution. I am about 80 miles from an Apple store and going there is not at all convenient. I do have Apple Care but wanna try to resolve it before taking the computer to St. Louis. I live in Southern Illinois. Thanks!