[Koha] Searching Authorities

Hi all Some time ago I imported some authority records using bulkauthimport into my Koha (witch I have set up unsing the defaults of the english installation). I did a rebuild_zebra.pl -a to build the zebra indexes. Searching a record I have some strange mistakes: I find the records using the point "Search main heading" but I don't find any using the other two possibilities (Search Authorities, Search all Headings). The same happends if I'm working on the biblio records and I try to connect a biblio record to the corresponding authority-record. I have to use the second possibility (Main entry) and can't use "Main entry (only $a)". I guess I'm missing some zebra-configuration. Any idea where to look? Beda