Thats odd as fences config being Black was one of the fixes in the latest WB update.
What can I say? I uninstalled Fences 4, ran the purge .bat, rebooted and reinstalled Fences 4, rebooted...but the *poof* didn't occur.
If there are no other ideas, perhaps the light background option (i.e. forcing a white background) might work?
A separate question: Would Fences 3 have this problem with WB11? If not, perhaps the difference is causing the problem?