[TYPO3-calendar] category icons showing up with file name instead of icon in backend

[Steffen Liebig]

Hello there,

I just entered a new event - when choosing the calendar, the categories 
are shown with the name of the file instead of the icon - like this:

-> t3-icon t3-icon-tcarecords t3-icon-tcarecords-tx_cal_calendar 
t3-icon-tx_cal_calendar-defaultKalender
   -> t3-icon t3-icon-tcarecords t3-icon-tcarecords-tx_cal_calendar 
t3-icon-tx_cal_calendar-default --checkbox-- category name

and so on in the category tree...

I'm using cal categories, maybe I should change to sys categories. Will 
possibly do so when I got time.

Btw - up to now, the category tree has been doubled e.g. once without 
showing the sub-categorization and once in the normally known tree. 
Choosing one of them, the belonging category in the other "tree" was 
chosen automatically. Same procedure for unchoosing.

Strange...does anyone know what this means and how it can be "normalized" ?

Thx for hints

Steffen