My permalinks are no longer working

Something happend in my multisite, but now the permalinks are no longer working with this structure: /%category%/%postname%/
Only with the default: … mydomainame.com/?p=123

I desinstalled the domain mapping and other plugins, but no result. Also after reactivating the plugins.

Nor I can set 777 to all sub folders of blogs.dir. Perhaps there’s the issue.
Hope you can help.

Thanks.