Hi,

In case of someone else got this problem, I found a (brutal) solution:
1) dump your selfoss database: mysqldump -u selfoss_user -p selfoss_database > dump.sql
2) drop your selfoss database (in mysql, root user): drop database selfoss_database
3) recreate your selfoss database (in mysql, root user): create database selfoss_database
4) restore your data: mysql -u root -p selfoss_database < dump.sql

That worked for me, I didn't search further.
jidey