Skype doesn't save any settings

Hi. I was using Skype Portable for about a year without any problems. But yesterday, suddenly, when I launched it, it showed me default blank welcome screen, like when you start it for the first time ever. Login drop-down list was empty as well and "Sign me in when Skype starts" check box is empty and greyed-out! So I can't check it. When I'm entering my login and password it logs in without problems, but doesn't saves any settings or history or whatever. When I close it and restart it again, it shows me the same initial welcome screen without my credentials and all settings are reset to default.

It really looks like for some reason it doesn't save any settings and sets everything to defaults, each time I start it.

I tried to upgrade to latest version and downloaded it from this site one hour ago. But new version has exactly the same issue!

What could be the problem?

Thanks.