Had to look up TortoiseSVN. Never heard of it before, but a line in the 'About' on their website made a few alarmbells go off:
"It is implemented as a Windows shell extension, which makes it integrate seamlessly into the Windows explorer."
That sounds like something that -might- have a thing or two to do with your issue.
If possible, try this:
Since it only affects Windowblinds skins, exclude the TortoiseSVN .exe file from within the Windowblinds config, from being skinned at all:
Apply chances, and maybe do a reboot.
