Ups....
I have to apologize 1000 times. I was working on three issues at the same time and mixed them up in my brain (it's time for vacation, i guess)
One was fixed in fact by changing the CSS, but this issue here....yes, i added the line <%...%> in the corresponding / used ascx-file of the skin. And then the panel won't appear.
However, when the panel is hidden, the users normally having rights to add events to the standard event-module from dnn, can't add events as the "link" in the lower left corner of the module is hidden, too.
For testing purposes i removed the line from the ascx, so the panel will appear for non-admin-users if there is a module (like events) on the page and then the "Add Event"-Links will come up when switching first to Edit-Mode.
Even when i'm logged in as the admin, the Panel will be visible of course, when in View-Mode, i cannot add events. I have to switch into Edit-Mode.
Strange effect when setting the cache time to -1 and in view-mode, only the module frame will stay visible, the whole month view (set ot "only view") won't be visible.
Again, i'm using the standard Event-Module from DNN in the latest version.
And what (not only) i wanna have is that if an user has the right to add events he just should has it without clicking on Edit. The Panel shouldn't be visible at all to everybody (but the admin).