http://bugs.winehq.org/show_bug.cgi?id=11657
--- Comment #12 from Dmitry Timoshkov dmitry@codeweavers.com 2009-03-15 23:46:14 --- (In reply to comment #11)
When that box is displayed under Windows (Vista SP1), the 'Cancel' button doesn't have an accelerator and 'C' is used for the 'Continue' button.
That's a simple patch for dlls/user32/resources/user32_En.rc, feel free to submit to wine-patches.