It is showing large slides and I change to medium size. Close EW6 and reopen to large slides. This is a new behavior.

Is this in the live area? I'm not having this issue. It sounds like it cannot save the changes to the settings file.
Might try renaming the windowsettings.ini file at the following location on your hard drive and then reopen EW 6 and make the changes.
C:\Users\windows user account\AppData\Roaming\Softouch\Easyworship.v6.1\Settings

I deleted the INI file and came up at same size. Changed to tiny and used Alt-F & X, Alt-Space & C and clicking on red X to close EW6. Still returned to same thumbnail size. Looked in INI file:

[list:3fk7836s][SlideSelector1]
LedgerView=0
UserZoom=50
[/list:u:3fk7836s]
I changed zoom to 25 and saved, so it's coming up at that setting regardless.