database error when saving style
 

I just made a new child syle (changed colours only). When I try to save it, I get:

Database error in vBulletin 3.8.3:

Invalid SQL:
...
MySQL Error : Duplicate entry '.fjdpth0-77-css' for key 'title'
Error Number : 1062
...
MySQL Version : 5.1.30

Help? I tried rebuilding unique indexes, but to no avail.