Ok, so sometimes on one of my computers when I boot up I get white areas on the taskbar. The main culprits are the start button and the button on the right that expands all the loaded icons (eg. volume control). Basically they have a box of white colour around them (I think using white rather than transparency by the looks of things). If I then run WB and apply the skin again then everything is fine. It happens on all the main themes I have used for a decent amount of time.

I'm using WB5.5 on XP Pro SP2.

Cheers