I'm getting an error pretty randomly where a box pops up saying, "Action Not Supported" and then the game quits and I'm sent to my desktop.

Is anyone else experiencing this or have a fix?

I get this when I alt+tab out of the game and alt+tab back in. When I'm back in the game it doesn't give me the action not supported bit until I click somewhere on a button or a unit. So if you're having the same issue as I am you're temporary solution is to not alt+tab.

Thanks for the reply. It's a start!

+1 for the Alt-Tab being the problem

I came here to see if anybody else got this error. And sure enough, I realize that I got it shortly after I had alt-tabbed to another window and then came back.

So I found a fix:
The problem is a conflict with DirectX while it is trying to transverse between your computer's native resolution and the game's resolution. This can be solved here:
http://www.closecombatseries.net/CCS/modules.php?name=Forums&file=viewtopic&t=11996

Following the steps found there can even let you play in windowed mode if you so desire.

Thank you!

Hey there, sincere apologies for the necro, but I'm having the same error and the link you posted seems to be dead. Don't suppose you remember what needed doing at all?