Some buttons are blacked out.. Rated 5 out of 5 stars

Looks good on tbird 15. Question:

I am using a custom theme on windows 7. The minimize/,maximise, close button on right is blacked out? Any reason for this?

This review is for a previous version of the add-on (3.5.2).  This user has other reviews of this add-on.

What do you mean by blacked out?
What custom theme are you using?