Plugin settings lost


I've got a hugh problem with my plugin settings. Evertime when I change the settings for one plugin, other plugin settings are lost.

E.g. when I set Riverdashboard as default dashboard the settings for twitter login and izap_videos are lost.

When I set the twitter login settings, the fbconnect and fistloginredirects are gone.

fbconnect -> tidypics -> userpoints_standard

and so on and so on.....

It seems to go round in circles.

I've disabled and enabled the plugins, reordered them but no effect.

Any suggestions?