not sure of it was fixed or not, but wasn't there a problem with flash player crashing along with the system when flash player utilized GPU decoding? I remember having a few crashes with WoW when I was running some video on youtube or some other site that usess flash player.
So that could be why some of you are/were crashing when boxing and multi-tasking at the same time.

my opinion on how much memory you need depends on how your system is configured. If you have 16GB of memory, but allow your anti-virus to scan in the background, let a defrag program defrag disks in the background, and have these other non-essential programs running in the background when gaming, all the memory in the world will not help. Simply because the cpu may be doing more work handling the strain from gaming and these other apps.

But a minimum I would use for gaming is 8GB, just because memory prices are so damn low at the moment you can not pass up these deals. If you are deciding what memory speed you should get, it depends on your cpu and motherboard. I have a sandy bridge 2500k and the supported memory is 1066, but my motherboard allows me to use 1600 memory speeds but this will overclock the cpu a little and cause a increase in memory voltage. So refer to your motherboard and cpu vendor before getting something.