eM Client Not Working. It is failing to show the mail folder.

When I opened up my computer this afternoon, eM Client is failing to show mail or my inbox. I am getting the following screen:

I cannot read or organize my mail, and if I close it again, I cannot reopen the application without having to restart. What might be the problem?

Thanks

this is an old post and there was no reply. an old friend of mine has now the exact same problem.
i was able to help by restoring from a backup but after 2 days the same thing happened. does anybody have any experience with this - and a solution to the problem?