Hello,
if it asks for groupware account password it asks for your password to your CalDAV account (menu Tools->Accounts->click your problematic account and CalDAV tab). Did you update password also for the eM Client CalDAV account or have option Use identity credentials enabled ?
Thank you, your suggestion has indeed fixed the problem.
I have forgotten that Calendar uses the same account.
Regards,
Marko
PS: For some reason this forum forgets my login info.
I came here this morning and I was logged in automatically.
Now I came to post reply and I had to go look it all up again. Weird.