There was a bug reported that after certain flashes, the N800 would still be stuck on opera and not microb.

Load Xterm and type

grep engine ~/.browser

it should say engine=microb, if it says engine=opera you need to change it.

Once source said to type this in x-term
perl -pi.0 -e 's/engine=opera/engine=microb/' ~/.browser

and a second said to type

cp ~/.browser ~/.browser.bak
cat ~/.browser.bak | sed "s/engine=opera/engine=microb/" > ~/.browser

I used the latter and no more crashes for me.