Created attachment 120319 [details] screenshot tested under Win7x64 using LibO 5.1.0.0.alpha1+ Build ID: db6a928a420868b2a80ba11c8d46151d16c13624-GL TinderBox: Win-x86@62-merge-TDF, Branch:MASTER, Time: 2015-11-05_22:13:24 Locale: it-IT (it_IT) to see this bug you should enable OpenGL from "Tools/Options/View" menu then just click on any dropdown menu of the LibO UI and you will see that menu will show up completely black for an instant (see screenshot) if you disable the OpenGL the bug disappears. this issue is not present in LibO 5.0.3.1
You seem to have the same situation as me, so closing as dupe and confirming my older report. *** This bug has been marked as a duplicate of bug 94843 ***