I read that this was solved; however, it happens to me about every 90 minutes. The time it takes to “repair” and restart is killing my workday. Is there another solution? 
Hello Tim, what mail service are you using with eM Client, can you please try to install this update, 6.0.22465.0 and perform folder repair on affected folders where an attachment can not be downloaded? In order to repair the folder, right click the folder in the left pane and select Properties > Repair and click on the “Repair” button for the folder to re-synchronise with the server.
Please make sure to let us know if the issue persists, or make a screenshot of the issue for more information.
Regards,