Looks like /data is not accessible.
Did you format, delete any /data while switching from slimkat/4.1.2 roms ?
Log in to recovery and then under Advancec-> File manager try accessing /data mount and see if you can access it ?
If you can access it then /data is not corrupted and it can be fixed by simply formatting it.
If not then I am not sure if there is any choice other than try to format /data and see if this fixes the issue -> Please note by formatting /data you will loose all your data and settings.