Hello,
I'm the proud owner of an N900, and despite having any knowledge about linux OS, I've managed to do just fine, till' now.
A few days ago i've installed a program wich turned the normal Nokia keyboard layout into a plane old PC keyboard layout. You have to hold down the shift / fn button when you need to tipe CAPS or using number mode.
It is awful when writting an sms.
If anybody can help me with switching back to the original layout, please do!
10x all!

I think you need to tell everyone what programs or downloadable package you used to get into this situation.

The next firmware release is going to come out in the next couple of months which will allow you to do a full reset of your device really easily. A bit extreme perhaps but maybe as a last resort?