[Users] claws mail hangs with imap stream error

[U H]

As in the subject: Suddenly, claws-mail does not connect anymore to
*ANY* of my imap servers and gives me an IMAP Error <name of imap
server>: stream error.

Since icedove at the same time connects and sends and receives
flawlessly i think that might be in some way something claws mail cashed
in a bad way. Reboot does not help.

TIA for any suggestion.