Just had a hell of a scrap with my 900 after trying Firefox...... again. Once installed it started OK but then the brown, smelly stuff hit the high speed cooling device.

First off, no matter what I did I couldn't stop it from using positioning, (had to restart the phone to shut down the GPS connection) it quit back to desktop before I could select an AP to connect through, (yet Conky actually listed Fennec as running), then MicroB also failed to start and I had no access to Ovi Store. My App manager also went ape (couldn't find any repos) and I was constantly switched back and forth between "Dual Mode and 2G" resulting in "No cellular connection available" error messages when I was trying to use Opera.
In the end I just did a restore to an earlier backup.

God knows what happened. But at this stage I've got my MicroB and Ovi Store back and I'm thinking 'Better the Devil you know'.