Hidden "Manage Event" popup in frontend

Hello,
if I click the "edit event" button in the frontend the page goes black and for one second I'll see the "Manage Event" popup. Then the popup disappears.

I'm grateful for any hint how I can solve that problem.

PHP Version : 5.6.0

MySQL Version : 5.1.73-1+deb6u1

Server Information : Linux eden5 2.6.32.60-grsec-netclusive #1 SMP Mon Jan 14 13:44:23 CET 2013 x86_64

Fix jQuery? : Yes

Load JEvents Bootstrap CSS? : Yes

Max Input Vars ? : 1000

Club code set? : No  

User Agent : Mozilla/5.0 (Macintosh; Intel Mac OS X 10_11_1) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/46.0.2490.86 Safari/537.36  

Joomla : 3.4.5

component_com_jevents : 3.4.4

component_com_jce : 2.5.11

module_mod_jevents_cal : 3.4.4

module_mod_jevents_custom : 3.4.4

module_mod_jevents_filter : 3.4.4

module_mod_jevents_latest : 3.4.4

module_mod_jevents_legend : 3.4.4

module_mod_jevents_switchview : 3.4.4

plugin_content_jevents : 3.4.4

plugin_finder_jevents : 3.4.4

plugin_system_gwejson : 3.4.4