Wich version are you on?

That's a problem (I think is a sort of bug, because the value is declared twice) into the
Style.css file of the template. Open it with a text editor and search for the
background: value into the
comments-inline-edit declaration (keep in mind to search for all of the declarations: there are many and the backround value it present in two).
REMEMBER: Jcomments 2.3 is
not FULLY compatible with previous version's templates!
