The first alpha version of the 0.39.0 releases introduce a new version of the settings file, which is located at '%LocalAppData%\Jojatekok\MoneroClient.Net\user.config'. Please delete it, or if you want to keep your settings while downgrading, just open it in a text editor, and change
into
. Also, don't forget to relocate
softwareWallet="Resources\Software\rpcwallet.exe" into
softwareWallet="Resources\Software\simplewallet.exe".

As for your rpcwallet issue, I will look into it deeper as soon as I have access to my personal wallet at home, so I will be able to test things more toughly. It is weird that the password request box doesn't show up - some people said that it happens since v0.36.0. Do you have any problems with v0.38.1? If so, does v0.35.0 or even v0.36.0 work for you?
Thanks, this works. Maybe there should also be a path option for this available in the GUI?
Just tried 35 & 36, like 38.1, they seem to work fine. Only with 39 builds, password request doesn't show up.