Opera 9 sets certain settings to defaults

Hello,

During the last couple of months I've experienced Opera ditching some
settings to defaults. This includes:
1. setting skin to default (was Odyssey)
2. setting progress bar to `Simple'
3. changed front to a different one when showing a certain web page
4. clicking on a tab again stopped to switch to previous tab

Resetting settings may not be limited to those, as I am describing
only those that I'm sure have happened.

1 and 4 have happened after upgrade to a 9.5 or 9.6 version at work.
1, 2, 3, 4 have happened yesterday, when Opera became quite large (>
600Mb of virtual memory). During that time, it also stopped showing
pictures it was showing before and complained it couldn't save
opera6.adr (if I remember the file name correctly). After restarting,
some settings were set to defaults. There was enough disk space in /
home and enough of virtual memory.

How can I fix problem 4? I've tried to run Opera with no .opera/
present and it didn't help.