Frequently, when saving an email, the cursor appears as a highlight in the folder list, not an arrow. That makes navigation ddifficult. V 7.2.37929.0
I am currently testing the beta version, and it is not like that. I also do not remember it being like that for me in version 7.
eM Client does rely on a fully updated OS, as there are some things from Windows that it uses like .NET. Two things you can try are to firstly make sure your Windows version is fully updated, and secondly you can download the latest version 7 release of eM Client from the Release History. The version 8 beta is also available to download from there if you want to give it a try.