Silverlight on Lion keeps hanging my computer.

So basically pretty much anytime I'm watching Netflix or Amazon Prime on full screen, the system hangs - the video always freezes, and the audio either continues, or it starts looping like a broken record. Requiring a restart. This has been happening since I bought the machine over 18 months ago. Running a Macbook Air 13 mid-2012 with OS X 10.7.5 that came pre-installed.

The "Authorized Apple Reseller" in my town replaced the logic board, thinking it was a hardware issue. Still having the same problem. Now the Apple Reseller Genius is telling me I should install Mavericks.

I've read all the forums online, nothing has fixed it. It surely must be a software issue. I've never posted on a forum before, but this is my last resort, because even the "Genius" can't help me get Silverlight working on Lion. Is he right? Should I take my chances with Mavericks, even though every forum online warns about the dangers of upgrading to Mavericks (battery life, especially, yo)?

Your thoughts?