[Koha] Error trying to do a ordinary search into catalog

Hi people! I am using Koha 3.00.5 in Debian Linux box. My configs are attached. Everything looks fine, but I can't search anything in my catalog. When I type something, say a topic or subject like 'engineering', or part of book title I get this error message: Can't call method "as_usmarc" on an undefined value at /usr/share/koha/lib/C4/Search.pm line 2386. Note that this subjects and books does exists in my catalog. As I sid, everything looks fine.... Any ideas?? Thanks in advance. Leonardo -- Sistema de Antivirus do CEFET-MG: Esta mensagem foi verificada pelo sistema de antivirus e acredita-se estar livre de perigo.