I had the N91 firmware blues. I was having the theme reset problem and various other weird problems (including a beta version of ShoZu crashing randomly) reported by others as a problem with the V1.00.028.13 29.03.06 RM-43 version of the N91 firmware that I have (apparently V1.10.030 05-05-06 RM-43 and newer versions fix these problems as reported at mobile 9) until I reformatted the hard disk.
Fingers crossed, things are working now (for me a phone isn't working until ShoZu works :-) ! ). It looks like my problems were due to one or more of the following
- the firmware version
- the Nokia podcasting app (which is in beta)
- the Nokia Wireless Keyboard app (which doesn't officially support the N91 but I was assured would work)
- puTTY series 60 v3 beta or
- the ShoZu beta
which were the only apps I had installed (and yes I am well aware as an ex developer of the perils of running beta software which is why I am not flaming or blaming anybody :-) ! ).