Fri Sep 5 13:02:56 CEST wafl.dir.size.max:warning: Directory /vol/vol0/users/luser/.thumbnails/normal/ reached the maxdirsize limit. Reduce the number of files or use the vol options command to increase this limit.
Huhu. There were actually 2 x 135k files under this users's ~/.thumbnails/normal and .thumbnails/fail directories 
This is RHEL 4.5, there's already a bug about it (i can't find it, but i'm subscribed to it).
I can see that ext4 raised it's dirsize limit from 32K to 64k, looks like it's not enough