I actually find I suddenly started having huge problems with one of AVG's most recent updates in a similar fashion. I originally thought it was a Windows update, because I updated both on the same day. The symptoms:
Any pages with Javascript or Flash on them had random code splattered across the screen and refused to show their contents, pictures appeared as though they'd broken mid download (multi-coloured stripes or pixels making up the remainder of the image) and so on and so forth. Also streamed video content of any sort caused Internet Explorer, Firefox and Chrome to crash, all the above symptoms were the same across all 3 browsers.
I've no idea what they changed in AVG, but it seems to be scrambling any and all code received. Removing AVG fixed the problem, not really sure if this is related to the OP or not, but it may be worth looking into.