Your issue is because you tried to remove the CMS. As I specified already, you WILL have problems on your forum is you try to remove the CMS. The only way to fix the issue is through the database now.
These are my notes from having to fix this issue for other users so many times...
Code:
Make sure all cms tables are gone.
Check package table to make sure no vbcms.
Check product table to make sure no vbcms productid.
Check productcode table to make sure no vbcms productid.
Check productdependancy to make sure no vbcms productid.
Check upgradelog and remove all vbcms script rows.
Then run upgrade.php script again.
Do NOT do those steps on a live site first. You should ALWAYS do queries on a test database first to make sure you don't break something.