[TYPO3-calendar] htmlArea and Cal-Frontend-Editing: Not working

[PM]

Hello everyone

When I activate Frontendediting in Cal then each element has the 
"description"-field. And this uses the internal editor (in my case: 
htmlArea).

Now the problem is: This discription-editor window only appears 
partially and can not be used.

Did I forget to add some settings or is this a bug in 
cal-frontend-editing or in htmlArea?



My Versions:
Typo3: 4.5.25
htmlArea RTE: 2.1.7
cal: 1.5.2

Thanks for your suggestions.
Patrick