ThinPro 6.1 / Firefox 49 update

We have an issue with the Firefox 49 update for ThinPro v6.1.

The URL box and other boxes have a black background with white text rather then the normal white background with black text with the previous version of firefox. the tabs etc also appear to have a very 'brown' theme.

Same Firefox 49 update on ThinPro v5.2 has the same 'theme' as previous versions of firefox i.e. white with black text.

I would expect the default theme to be the same for both versions of ThinPro

Any idea's ?

Regards