So, I noticed this starting probably around DMUC 6.2...basically both the campaign and the battle phases are very unstable, resulting in frequent crashes with no error (aside from Microsoft's standard "there has been a problem"). It's happened both before and after I recently formatted my main hard drive, as well as before and after completely reinstalling ETW.
My only lead at this point is that perhaps ETW isn't properly updated. I don't know why that would be since I'm running through Steam and any deletion and reinstallation should automatically update to the latest version. Alas, in the main menu the version signature is only 1.5 (Build 1332.21992)
Other than that the only consideration is perhaps graphics drivers, but I'm running nVidia drivers from early '10 (the latest ones are said to have problems of their own), so I'm doubtful of that explanation.