just problem is every post is “Not categorized”, i have about 550-600 posts 🙁
Manually take backup from old host’s PHPMyAdmin in SQL format, if you still have access to the old host. You will only need few tables => read my guide for manual method to clean WordPress database (ignore cloud things there, basics is the same). You will get as text files, Run as SQL query on new database. Probably wp_term_relationships table (or may be terms table too) has issues.
Automated backup failed as you have not optimized your database before taking backup. The data integrity has been lost. It is important to check the backup if working or not, before moving.
If you do not have access to the old webhost’s database, there is no way to build the relationship as the data is already lost.
These are a bit advanced usage, if you are not sure what you are doing, please ask your some friend or hire someone from http://jobs.wordpress.net/
Take help of peoples who are involved with WordPress software development for many years.
If you do not have access to the old webhost’s database, hiring will not help. If you have old backup in SQL format, check them. Open in Text Editor like TextEdit (Mac) or Gedit (all OS), Notepad (Windows) and find wp_terms, wp_term_relationships etc tables. Kindly do not use Word of Microsoft Windows to open them.
You will see they are actually in a human readable format.
