Here's the link for Stardock Support:
WWW LinkEmail link is about 3/4's down the page under "Still need help". Start up a ticket with them and reference this thread so you don't have to repeat yourself.
Probably save yourself some turnaround time if you include, either in the mail or by replying to this thread:
WinXPHome or WinXPPro32bit or WinXPPro64bit or Vista(bit and version)
Whether you're using the free OD or the paid OD (OD Plus) and which version of whichever it is.
Verify that it did come from Stardock, not a 3rd party site.
If you put that here in the thread, it might give someone else a better idea of what might be going on.
Older versions of Object Dock wrote the created themes into the program directory under C:\Program Files\Stardock\ObjectDock\(Themes-I think). Of course a standard Limited User arrangement won't let you write to C:\Program Files\etc., so that would cause failure. But, if you're seeing the new theme name saved in your Ltd User's My Documents, doesn't seem like that would be the problem. I don't know what the heck would cause it to save the new theme but with no parameters.
The other generic response would be if you're using paid OD Plus now, did you have the free version installed before? If so, did you uninstall the free version before installing the paid version? If not, uninstall the OD Plus (and the OD free if it's still showing out there), and try re-installing the Plus.