I'm on Win 7 64 bit, with 8G, and have had no problem with alt-tab whatever.  I did on EWoM, but not on FE so far.  And I'm constantly alt-tabing in and out of the game to check on these forums.

I noticed strange behaviour aith alt+tab, it might be coincidence but on 0.75 it worked every time: I get a crash when simply alt+tabbing out of the game. However, if I alt+tab out of the main menu before I start a game then I can alt + tab without trouble from the game. Have to check with 0.86

I have noticed that if you shift-tab first, alt-tab works better.