The problem relies on old themes and their corresponding INI file.
I recently had to fix the ini of the "Simple rounded" theme (the coolest one IMO) to be able to make it show on the styles menu.
Open the ini from a default OD2 skin and open the ini of the old skin then place them side to side, and try to carefully make them match together while retaining the values on the old one.
Here's the Simple rounded theme just in case you want to try.
www.spyro.mediashift.net/updates/Simple_round.zip
Extract the folders according to the structure I've put on the zip, probably is different in your system but there you go.
Cheers!