[Koha] Again: delete MARC records

[stefan]

Dear List,

I've imported different .mrc files using the graphical interface of Koha 
and was able to delete them with the  "undo import" button in "staged 
records".
Without manipulation of the source the "undo import" button desapeard. 
So I tried:

bulkmarcimport.pl -d -file zm42a_1995_2000.mrc

Now the extranet OPAC is down, giving the error:

Can't call method "leader" on an undefined value at 
/usr/share/koha/lib/C4/Biblio.pm line 1051.

In the Intranet OPAC the search results the records still apeare. When I 
click on a bib record I get following error:

Can't call method "fields" on an undefined value at 
/usr/share/koha/intranet/cgi-bin/catalogue/MARCdetail.pl line 124.

I ran rebuild_zebra.pl without success.

Can you tell me a method how to delete MARC records/items permanetely 
and savely?

Thank you.

Stefan

Specs:

Koha 3.01.00.052
Debian Lenny minimal
MySQL and Apache up to date

P.S. The Zebra features are just glorious!