I had this issue just like everyone for awhile and tolerate it until in big battles I lost since I can't micro since it FREEZES.
The issue is a combination of nVidia drivers and intel processors as I discovered on other forum posts. This solution solved my problem and there are no more lags.
Depending on which version of windows you have. Start -> Run -> services.msc
In the list of services, find these nvidia services and disable them.
"NVIDIA Display Driver Service"
"NVIDIA Stereoscopic 3D Driver Service"
"NVIDIA Update Service Daemon"
As the creator of this thread, I would like to personally thank you for your hard work and determination in fixing this major issue within the game of Starcraft 2. I just finished testing this fix, and it is working wonderfully.
While this whole incident hasn't exactly convinced me to purchase HOTS (or any new Blizzard game, for that matter) anytime soon, at least the game that I currently own that Blizzard refuses to take back is finally playable again. Time to practice, practice, practice! I'm completely out of practice in Starcraft 2.
I essentially completely removed myself from the entire SC2 community with the exception of this thread. I didn't even watch professional Starcraft 2 games or any Starcraft 2 YouTube videos. I'm not sure if/when I will return, but it will hopefully be soon.
Again, thanks a lot for your help and for providing a solution to this issue. I and much of the Starcraft 2 community are very grateful that you've been able to provide this fix.
I will now officially stop replying to this thread unless anyone really wants to speak with me on this matter (I will check back for the next few days before bookmarking and officially closing this tab). I ask for everyone to please stop bumping this thread-- it has a ridiculous amount of replies and views because I've been keeping it alive for so long, but it has finally served it's purpose (thanks to vipy).
If you followed vipy's steps but your issue is still not solved, then you are experiencing a different issue from the one mentioned in this thread. It is important to note that this issue is not just generic low-FPS or constant lag, but rather periodic lag every time a sound is played which was then reduced in patch 1.5.1 or 1.5.2, but still persisted in battles and battles almost only (I say almost because there was still some additional lag present). This lag still made the game unplayable.
This also only applies to users with NVIDIA graphics cards and Intel processors. For everyone else, both this issue and solution do not apply to you. Please start a new thread based around your problem.
Again, thank you so much vipy. It's unfortunate that Blizzard is too incompetent to have been able to figure this out themselves and posted it nearly two months ago when patch 1.5 was introduced. I have no plans to support Blizzard in any way in the near future after this incident. I'm just very happy that the product I purchased a while back which Blizzard refused to give me my money back for is now finally usable again.-Technology