preferece settings are lost

[JustInfo]

All preferece settings are lost after switching off and on again

[Gingerbread Man]

Do you use the Delete Private Data feature? If so, that's probably what's trashing your extension settings. That bug should be fixed in the upcoming Opera 12.12; see below for the test version change log.
http://my.opera.com/desktopteam/blog/2012/12/06/the-wait-is-over