[TYPO3-english] Error upgrading from 6.2 to 7.6

[Gunnar Jonsson]

I am trying to upgrade to TYPO3 7 and get the following error messages when running Upgrade Wizard and "Update database schema: Modify tables and fields"
Update failed!
Update process not fully processed. This can happen because of dependencies of table fields and indexes. Please repeat this step! Following errors occurred:
SQL-ERROR: Data truncated for column 'image' at row 172
SQL-ERROR: Data truncated for column 'media' at row 171
I repeated this step several times with the same result.
Any idea what kind of problem this is? And how to solve it?
Regards
Gunnar Jonsson