Hah, good to see people on Windows getting these out-of-memory related crashes as well.
That's not to sound mean or anything, but this has been the case on OS X for well over 1.5 years now, with the only way to make it playable being to lower texture detail to medium (and it then still uses well over 1.7GB where it used to use 850MB). Maybe this is the time where Valve finally gets going at fixing it once and for all for all platforms.
Your best bet is to email Valve about it. Give them as many details as you can. Crash reports, driver versions, everything. I'm working with this guy called sigsegv (who's a master at Source coding and has pointed out/fixed multiple bugs for Valve with the last couple of updates (including MyM) but he's busy at this time, so that has to wait for a little while.
