user warning: Duplicate entry 'xxxx' for key 'vid/PRIMARY' query

Hi

I used the latest vbulletin version, the latest vbtodrupal and the latest Drupal 6.20 release.
Because my vbulletin database is very big I only uploaded following tables:
- thread, post, user, pm, usertextfield, userfield, usergroup, forum, attachment, user, customavatar, pmtext, pollvote, attachmenttype

the content in _node starts with
nid vid type
1000001 1000001 forum

So far so good. Because I have a lot of entries, this goes on and on. BUT: If I want to create new content (page, story, topic, it doesn't matter), it wants to use small VID/PRIMARY Keys like "1000634" or in PRIMARY "0" which is ridiculous of course.

So I get this errors:

* user warning: Duplicate entry '1000634' for key 'vid' query: INSERT INTO _node (vid, type, language, title, uid, status, created, changed, comment, promote, moderate, sticky, tnid, translate) VALUES (1000634, 'page', 'de', 'Test', 1, 1, 1293808111, 1293808111, 0, 0, 0, 0, 0, 0) in /includes/common.inc on line 3538.
* user warning: Duplicate entry '0' for key 'PRIMARY' query: INSERT INTO _node_comment_statistics (nid, last_comment_timestamp, last_comment_name, last_comment_uid, comment_count) VALUES (0, 1293808111, NULL, 1, 0) in /modules/comment/comment.module on line 607.

I don't know why this happens, please help me asap,

thx