Grey restart and program crashes after logic board replacement?

Apologies for if a thread already exists for this, I had a look around and nothing seems to quite fit the problems I'm experiencing-

I recently got the logic board replaced on a 13-inch macbook pro, osx lion, 10.7.5. I got this done because of the failure of one of the usb ports and the centre row of typing keys.

however (although the keys and usb now work), after the replacement, I have started to experience problems that weren't present before. These include:

1. programs spontaneously crashing, examples being safari, itunes, and photoshop
2. the computer spontaneously going into the grey textured screen and restarting all programs, but seemingly not initiating a full shut-down and restart
3. itunes has deauthorised me and claims that there are already 5 computers authorised to the account. No new computers have been authorised during the repair time and attempts to deauthorise and reauthorise fail, this was not present before the repairs.
4. video playback on youtube and similar sites can sporadically cut out completely, either freezing or causing the entire video 'screen' to white out or vanish
5. playback of other moving graphics such as gifs often is jerky or replaced with transparent or white frames

I've updated all my software to the latest versions just in case it was simply that I wasn't up to date with something, but to no avail. Is this a common error with a solution, or am I going to have to get the logic board replaced again? I'm still within my three-year warranty, but I don't appreciate the concept that I brought in my machine to be fixed, and it came back even more broken.

(safari crashed during writing this, here is the crash report in case that helps)