Hi
I thought it would be worth mentioning that when you encounter a problem with DoW it's well worth checking out the game's developers forum at Relic.
There is a bounty of information there that could solve your issue which could possibly be a known problem with the game and not necessarily a problem with how Cross Over handles the game. So if in doubt, check there and here and hopefully answers can be found.
Relic's Dawn of War forums (the Technical help section is the best place to have a look)
http://forums.relicnews.com/forumdisplay.php?f=90
Sorry if this is a bit obvious, but all my initial problems were problems with the game, not Cross Over.