The title is exactly the problem. This problem appeared sometime in the last year (I have a 2006 version of the app that doesn't show the problem, but the 2007.1 and .3 both show it).
I have an MDI application with a couple of different forms, each with a C1List that shows a bunch of records. I open the first form, show the records, click the list's collumn headers to sort, no problem. Then I open the second form, show its records, click the column headers to sort, also no problem. Then I close the second form and the fun begins: when I move the mouse over the column headers in the first form's list, the mouse disappears and I can't click the headers. That's with C1List.AllowColSelect = True. Eventually, I can click around the list for a while and it'll crash the program with an exception in the C1List code.
When I set it to False, it works fine.
I have my fix, clearly. But it's going to bite someone else eventually, so I'm posting the problem and the workaround here.