If you have it one a sensitive button make sure nothing else in the background is set to that.
Aside from that, the Steam Overlay has been known to cause problems in the past. Personally, I don't have a problem with it in Skyrim, but it's quite possible it's causing a problem for you. Maybe try Fraps if the problem clarifies and you're sure it's the screenshot thingy.
About the LAA fix:
I only started crashing after I applied the LAA fix and I didn't notice a difference in performance. It didn't crash frequently enough to either pinpoint the first crash to the fix beyond reasonable doubt, nor to make me want to bother and "unfix" it. Now that it's unfixed the performance is still the same and I haven't noticed a difference in crashing yet either. As I said, it's not frequent enough for me to really say one way or the other, but the point about the performance stands, at least for me.
And I have a PC that's good enough that if the low RAM were a problem (and 2GB max, minus what the GPU is using, is incredibly low) that would most certainly be my bottleneck.
So without seeing a benchmark I have a hard time believing people who claim to have much better performance with the fix and much less CTDs.
Remember the same was said by loads of people after every tiny post-release RO2 update, if it actually did something about performance or not, even if it wasn't actually out yet or got rolled back again.
And a community-made performance fix is even more ignorantly welcomed by players, usually. Who doesn't like a Witchdoctor to swoop in with unconventional methods, especially if it sounds as logical as this one?
I'm not saying it does nothing. I believe it does what it says. What it doesn't do, however, is rewrite Skyrim to take advantage of this, let alone optimize it for this. The game doesn't seem to need more RAM so porting a program that made The Sims give access to more, for whatever good that did, lol, to make it able to access more won't help. At least not as much as we'd like it to.
Performancewise, and stabilitywise it just did nothing for me so I have a hard time believing it did something for anyone else until I see actual numbers, from a test, under testing conditions to - no offense to any of you - rule out the placebo effect that is oh so common with fixes like this.
I'm sure that once mods push the limits and the game will require more RAM at some point we'll start to see real benefits from this, and maybe it'll be officially fixed too at some point, but for now? Eh. Seems like much ado about nothing.