IDK if you have resolved this problem yet or not, but here are some tips to help:
1. You can't have any shortcuts on the taskbar
2. If you Right Click> Skin It! on the area the Finderbar is located, it will set it to the color of the taskbar.
3. I agree with nrossow. It is best to have the taskbar at the Top for the complete iMac theme.
I also have a problem with my Finderbar as well. If you have a color background, and you have transparency on, it makes the text unable to see (By making it the same color as the part of the wallpaper it is on top of) If you EVER have trouble with this, just Right Click on Desktop > View > Show Desktop Icons, it will take them off. and make sure you have the Taskbar in the right place. then take a "Snapshot" of the desktop, and open it in Paint, or PhotoShop and make the area were the taskbar is black. That way the text will see through the taskbar and see Black which makes the text Readable.
After you do that, just put the icons back on the Desktop. Hopes This Helped