I'm not an Object Bar expert, but I know what the problem is. It's to do with how the margins are set in the WB skin. I've noticed on some of my skins using Object Bar part of the Start Panel Bottom Bar is white instead of skinned. The skinned bit corresponds to the margin I set in WB. Of course, it looks fine in XP, but if you're using 98...
I'm updating my skins now even though the majority of people are using XP. I use 98 at work and it is annoying. Maybe you can persuade other authors to do the same, or do the tweaks yourself in Skinstudio.