KMail does not remember which Mail was already read

Hi, I have a nasty problem with KMail. In some folders (especially if the amount of Mails becomes >20) KMail does not remember, which mails have already been read. E.g. I read a new mail, Kmail marks is correctly as read. After restarting KMail exactly this mail is marked as new. This Problem accours only in a few folders. The Mailbox is in maildir format (and was created by KMail 1.4). In the mailbox, all mails, that have been read are in the folder cur but they are not recognized as already read. Is there a workaround for that problem? best regards -- Stefan Rauch public-key: http://www.stefan-rauch.de/pubkey.html pgp-fingerprint: E72F 2B21 88CF 8641 5F82 0B4D DD6B 8383 92FE 88E8