After migration problem 2.0.14 to 3.0.7_01

Hello,

We experience following problem after migrating from rt-2.0.14, postgres 7.1,
perl 5.6.1, apache 1.3.27 to rt-3.0.7_01, postgres 7.3, perl 5.8.2, apache 1.3.29
on debian using rt2-to-rt3 script:
all tickets, users, queues are in place but we can not perform some operation
existing tickets (comment, reply) or create new tickets.
We get the following error message:

Dec 4 15:20:53 tracker RT: DBD::Pg::st execute failed: ERROR: duplicate
key violates unique constraint “tickets_pkey” at /usr/lib/perl5/site_perl/5.8.2/
DBIx/SearchBuilder/Handle.pm line 410. (/opt/rt3/lib/RT.pm:247)

Have anybody seen that before ?
Any ideas what went wrong/should be corrected ?

regards from Poland
Jacek