I'm sorry if tech support is outside the context of this site. If so you may close this question.
Just recently I've started getting lag spikes. I used to get this lag spike all the time but only whenever a new player joined my party game. But just recently few days ago when I started the game, the game would constantly freeze for 1-2 seconds every 15-20 seconds, and then start moving again very quickly to catch up with the things that happened during the freeze. I haven't changed my graphics card drivers, or did any hardware changes. All I did was install Path of Exile, but I'm not sure if that could have screwed up my Diablo 3. It took me quite a while to download and install updates on Path of Exile so I don't really want to try uninstalling it until I've tried other things. So far I've tried changing my graphics card settings (Catalyst 3D and Video settings), lowered everything in-game, even checked the "Low FX" checkbox. I've also tried Repairing Diablo 3 which didn't help.
I have a slow connection (2Mb) but it's enough to play the game at 65ms constant. I've used CTRL+R and didn't see any stutters in FPS when I get the lag spike. Because of my slow connection I also didn't want to re-install Diablo 3 without trying other things first.
CPU: AMD X2 7850 Black Edition stock clocking
RAM: Kingston HyperX 4GB dual channel stock clocking
GPU: ATI HD4850 512MB RAM
OS: Windows 7 64Bit