as a first step, I suggest reading the event log .  it will tell you usually if you are having a problems a startup service that is timing out, for instance.

Well, if you did copy your 9.1 profile prior to the install/upgrade, then you should be able to revert back to 9.1 without a problem.

I *ALWAYS* backup my program files/opera folder before re-installing or upgrading (along with the profile it is is located in your application data folder instead of within the root program folder).

I also recommend UNWAND to decode your wand file into a text file in case you ever need the passords for another browser ....there is no export/import to my knowedge (would probably defeat the purpose).

http://speedman.sk/17operawanddatenglish/

Since Opera uses little or no registry entries (except if it is selcted as the deafult browser for OPEN WITH entries), then reverting is simply a matter of copying the files back in place.