eM Client freezes after changig the port-number of an imap-account

I use the version 7.0.27943 on a Win7-Computer. For an installation of an imap-email-account I have to change the imap-port-number from 143 to 993. But everytime, when I do this and want to click on ›ok‹, the programm freezes, so that the change is not completed. What can I do?