internal warning: bad request for InternalUnsigned

hi,
When I use bro-0.9a9 on a linux system,there’s lots of warnings on the screen:
1120748634.654520 (768): internal warning: bad request for InternalUnsigned
1120748634.654520 (769): internal warning: bad request for InternalUnsigned
1120748635.289065 (2): internal warning: bad request for InternalUnsigned
1120748635.289065 (768): internal warning: bad request for InternalUnsigned
1120748635.289065 (769): internal warning: bad request for InternalUnsigned
1120748635.291004 (2): internal warning: bad request for InternalUnsigned
1120748635.291004 (768): internal warning: bad request for InternalUnsigned
1120748635.291004 (769): internal warning: bad request for InternalUnsigned
1120748678.874703 (2): internal warning: bad request for InternalUnsigned
1120748678.874703 (768): internal warning: bad request for InternalUnsigned
1120748678.874703 (769): internal warning: bad request for InternalUnsigned
1120748678.876645 (2): internal warning: bad request for InternalUnsigned
1120748678.876645 (768): internal warning: bad request for InternalUnsigned
1120748678.876645 (769): internal warning: bad request for InternalUnsigned
1120748678.930197 (2): internal warning: bad request for InternalUnsigned
1120748678.930197 (768): internal warning: bad request for InternalUnsigned
1120748678.930197 (769): internal warning: bad request for InternalUnsigned
some one tell me why?