It was from WPML ?1.1.8? to 2.0.0. I can't remember the previous version exactly, only that I installed it within the last 2 months.
It took so long to upgrade the database that I forgot about it and accidentally closed the window. When I went back into the wordpress backend and checked WPML, everything seemed to be okay and working.
However, I'm still worried. How do I check and make sure that the database really is okay?
http://wordpress.org/extend/plugins/sitepress-multilingual-cms/