Hi, I have the same issue but saving is not possible in any case.
I have checked a lot of things like rights, and created a complete new calendar as well as categories but sill not able to serve.
And during my research in the net, there are several other who has trouble but with strange bugfix.
Here is the system I am working at:
Domain: naturistenbund.de
PHP Version : 5.3.10-1ubuntu3.18
MySQL Version : 5.5.43-0ubuntu0.12.04.1
Joomla : 3.4.1
component_com_jevents : 3.2.12
module_mod_jevents_cal : 3.2.12
module_mod_jevents_custom : 3.2.12
module_mod_jevents_filter : 3.2.12
module_mod_jevents_latest : 3.2.12
module_mod_jevents_legend : 3.2.12
module_mod_jevents_switchview : 3.2.12
plugin_content_jevents : 3.2.12
plugin_finder_jevents : 3.2.12 (not enabled)
plugin_search_eventsearch : 3.2.12