black (instead grey) playlist button in editor window

I am trieing to select a playlist on an active track in the main editor window, but the playlist button-as well as the record button-seems to be “dead”: they appear both black instead of the normal grey. The m-s-a-g buttons can be selected as normal.

Any ideas?

MacBook Pro 2.53 Ghz Intel Core i5
Mac OS X 10.6.3
Ardour 2.8.11
MIO Console 5
Metric Halo 2882 2d expanded

any chance of a screenshot showing this?