I just bought ODNT based on their good history and had the problem of getting the classic style as soon as I installed WB5. I've been reading thru the forums and while I found others with a similar problem, none had a fix. I finally fixed mine so maybe it will help others.
I had the latest ATI drivers loaded, 5.13, for the Radeon series. I decided to roll back to an earlier driver as I had had issues with the DotNetMessenger window error coming up on shutdown and it was related to the 5.13 drivers I found out. I decided to reinstalled the 5.11 drives to see if it fixed both problems and WB5 started working just fine. I am now able to apply skins and I no longer get lockups or just the classic theme. It appears to be a compatiblity issue between the 5.13 drivers from ATI & WB5.
FYI.