XBill crashes ReactOS on exit with "Assertion 'Class->cWndReferenceCount == 0' failed"

Created an attachment (id=7565)
ReactOS crashing when XBill is closed

Upon exit, XBill 2.16 will crash ReactOS. In the debug log, the last line before the crash is: "Assertion 'Class->cWndReferenceCount == 0' failed"

XBill and source can be downloaded here: http://www.azzit.de/xbill/

There is also a problem with the content of the main window not rendering, but that may or may not be related.

XBill used to work fine under ReactOS, but this was so long ago that it is not possible to regression test.

Attaching debug log. Tested under bootcd-56283-dbgwin.