Problem editing/adding themes in Sharepoint Services

WindowsServices >> Problem editing/adding themes in Sharepoint Services

I get the following error when applying a modified theme to my Sharepoint
Team Site:

A theme with the name "TECUK 1011" and version already exists on the server.

This only occurs on the main/home site - I can apply the modified theme to
sub sites without problem.

Any help would be very much appreciated!

Many thanks
Ben

Windows OS196