Prob with IMAP and E-mail App

Hi,

I tried today to install imap to our server (because I want to migrate from
pop3). Imap (UWash) seems to work. If I use the Email-App (not Felami) of
phpgw (.003) I get the error:

Warning: imap_open(): Couldn't open stream {localhost:143}INBOX in
/srv/www/htdocs/phpgroupware/email/inc/class.mail_dcom_imap.inc.php on line
214

after clicking again on the Email-App it goes away and all works normal.
Writing and receiving Emails works. What could it be?

TIA
 Alex