Permission problems after upgrade to 3.3.5 only on index.pl

[fledeboer]

Hello,

today I upgraded OTRS from 3.2.15 to 3.3.5.
Now I get several JS alerts only on the agent dashboard. These errors are like "Error during minification of file /opt/otrs/var/httpd/htdocs/js/thirdparty/flot-0.8.1/excanvas.js: mkdir /opt/otrs/var/tmp/CacheFileStorable/CacheInternalLoader/2: Permission denied at /opt/otrs//Kernel/System/Cache/FileStorable.pm line 79".
Pages like index.pl?Action=Admin seam to work fine.

I already reseted all permissions with otrs.SetPermissions.pl. (as otrs user)
I rebuilded the configuration via otrs.RebuildConfig.pl (also as otrs user)
I deleted the cache with otrs.DeleteCache.pl
I restarted the apache.
I also dumped the mysql data and reinstalled the hole otrs 3.3.5 out of the tarball. And then imported the mysql dump.

The OS is Ubuntu 12 LTS. The otrs user is otrs, group =nogroup. The apache user is www-data and the apache group is www-data.
The otrs user is also in the www-data group.
The Permission I set with otrs.SetPermission.pl /opt/otrs --otrs-user=otrs --otrs-group=www-data --web-user=www-data --web-group=www-data
I chmoded the /opt/otrs/var/* to 775

Has anyone an idea what I should try next?

[crythias]

ls -lad /opt/otrs/var/tmp/CacheFileStorable/CacheInternalLoader

[fledeboer]

ls -lad /opt/otrs/var/tmp/CacheFileStorable/CacheInternalLoader

drwxrws--- 18 www-data www-data 4096 27. Feb 00:37 /opt/otrs/var/tmp/CacheFileStorable/CacheInternalLoader