http://bugs.winehq.org/show_bug.cgi?id=31914
--- Comment #1 from Henri Verbeet hverbeet@gmail.com 2012-10-08 07:40:48 CDT --- Flash isn't really helping if you want me to take a look, but from your description this sounds like something that would be affected by enabling "AlwaysOffscreen" by default. You should probably try disabling that and see if it makes it any better. (See also http://wiki.winehq.org/UsefulRegistryKeys.)
I don't think this is really a Wine bug though. If this only happens while using glc-capture, the most likely explanation is that glc-capture doesn't properly restore some GL state it modifies, or doesn't take some GL extension Wine uses into account.