Odd. Just the generic suggestions:
If you have any docklets running, go into OD's config - General, Troubleshooting Options Button, check "Temporarily disable all docklets" and see if the problem goes away. If it does, you've got a docklet in there causing you problems.
If you had Object Dock Free installed before you installed Object Dock Plus, the free needs to be uninstalled before you install the plus. If you didn't do that, back up your themes and any images you want to save, uninstall the plus, uninstall the free, reboot, and re-install the plus.