Can't read new messages - flash in the list and disappear

My client application has been updated today (14-Dec-2013) to version 6.0.19660.0 and now I have a problem - new unread incoming emails appear in the list briefly and then disappear. I can’t see or read them. If I send a message to myself I can see then including the ones when just disappeared. Close and open the program again - the messages stay now. Read them all and when start - new messages flash briefly and disappear. I checked with web client - emails are on the IMAP server. My phone can see them also. It was not a problem until the upgrade.

I have 9 IMAP accounts configured & Google calendar. I had no this problem before, although I had another problem - the application was hanging on refresh sometimes and I had to restart the application.

This is very annoying ans makes the program which I paid for unusable.