I have the same problem, very boring in deed, I beloved it was hardware before I read all yours specifications...
I don't think it is Hardware, I have a munch older specification then any of yours, 7800GT , AMD 2.8GHz and 1 G RAM I run graphic settings on normal (also tried high it works fine but crash more often).
I have seen a big improvement since I upgrade OpenAL and start use -maxmem=512 (visual graphic is worse thug)…I install 1.11 and all bad problems was back plus some new.
We all uninstall 1.11 in the clan and went back to 1.09, well it is better again but not as good as before---> the only thing I can see could have been changed is OpenAL, I will try tonight and see if it helps.