This happens to me occasionally and it has been happening since 2009.

I often use 'Q' the clipgroup function, but sometimes the option to unclip is grayed out when the clipped group is selected. However, if I press Alt + Q, the group will unclip anyway. I'm not sure what causes this. Sometimes, I save and exit the program and then can unclip. However, I currently have a file that will not unclip no matter what. I really wish that Xara would fix this. When I click on the group, it does say "Clipgroup Selected" in the tooltip.

Does anyone else have this problem? I guess I could open the clipped group, select all objects and create a new file, but what a pain.