Calendar Problem: There was a problem with the request.

Hello,

I've a problem (since a year or so) with a dav groupware ressource.
I get always the status-message:

"There was a problem with the request. The item was not modified on the server.
The file or folder secret.example.de does not exist. (0)."

I delete the ressource and add them again several time it works for some time/minutes, and then I got the error above.
Can someone help with with this issue?

A year ago i tried to add a ical-file which doesn't work, I guess since this I've these problems. The file does not exist anymore.

Best regards
Stefan