All three attempts to exit the running client to read an e-mail or load a new song on Itunes etc. crashes the client every 10th or so time. It's very unreliable. Earlier in the years 2010 and 2011, I was perfectly able to switch with Alt+Tab, now that doesn't work almost at all. Windows button on the keyboard works a bit better, but not very reliably either.
This is really annoying. Every other game I play works fine with alt-tabbing or windows-pushing.
It doesn't matter actually. I can have an internet browser window open next to the game app, or just nuffin, or a bunch of other tabs. It crashes randumly and it can happen anytime. So better don't exit the client at all, as long as you want to make sure the mission is suxxessful.
I have only had this issue with a multi-monitor setup when one of the monitors the game is running on is hooked up to the same graphics card as another monitor. Then I get some kind of out of graphics memory crash.
When the game monitor is run off its own graphics card I never get this error.