I have the same Red X problem. As the guy that stated he had 2 red X's...
I have uninstalled Decal and ElTank 3 times. Re-installed, updated re-installed. And it still doesn't work. I have even gone as far as Installing .NET 2.0(Release) instead of the .NET 2.0(Beta 2) that I had.... and... NOTHING
My next step that I can think of is to completely whipe all decal and eltank off, reboot, then proceed to re-install. If this doesn't work... I have no clue what to do.... Make my own Decal?