Guild Wars 2

This occasionally happens for me as well, exactly as you describe, but only lasts for about a second or two before everything displays correctly.

Task bar effects: My laptop only has 4 GB of RAM, but I decided to try the 64-bit client just to see if I could spot any differences in performance or behavior. The only difference I’ve noticed is that, when using the 64-bit client, my Windows task bar does not bug out. (After playing Guild Wars 2 with the 32-bit client, the task bar acts as if the mouse is always hovering over it, highlighting icons and displaying tooltips when in fact the mouse is not near the task bar.)

I have not tried the 64-bit client with the single most FPS eating event in the game (in my experience), Frozen Maw, yet.

Concerning lag spikes: The game would occasionally freeze while playing on the 32-bit client on my laptop with 4 GB of RAM. After some investigation, I discovered that the freezing occurred whenever Chrome was updating itself and whenever Windows Update would automatically start checking for updates, both of which use a considerable portion of my memory. Closing Chrome and (not recommended) disabling Windows Update solved the issue for me. (This is not feedback on the 64-bit client, and I only include it for the sake of those who report here getting lag spikes on both 32-bit and 64-bit clients, as a possible source.)