Pomoc 15.6 & 16.0 / both -> Bad response from server: (200 [parsererror,list])

LoCrux

Passing Basics
Beginner
7 Styczeń 2016
29
5
3
QNAP
TS-x53
Ethernet
1 GbE
As the title says; I get for both versions the message "Bad response from server: (200 [parsererror,list])".
After reverting back to version 15.5.002 everything works fine again.
Standard procedures taken: Browser cache cleared, NAS reboot, etc... Nothing works to get 15.6 or 16.0 running.
I have about 4000 torrents in my share!!! Once I also got the message (something like) "error in line 4" for conf.php (maketorrent) in "/CE_CACHEDEV1_DAT/.qpkg/rtorrent/var/www/ui/...????...very long path"

Your help is appreciated. :)