/user/cache/folder to be writable. Now it's solved by clearing the old cache in that folder.
I have also moved Karen's and Because I Learn to this new LEMP server. During the WP WXR import I had to change
memory_limitin addition to
/etc/php5/cgi/php.inior else I'll get
Allowed memory size of 33554432 bytes exhaustederror from WP.