Hi nikasp,
Using the external keyboard to reset PRAM is a good idea. If that doesn't work...
Let's do a quick test to see if this is a hardware or software issue. Insert the install DVD that came with the computer and restart, holding down the C key on your keyboard. When it finishes starting up, select your primary language and go to the next screen. Go to the
Utilities menu and select
Terminal. When the terminal window appears, type something in the window using the top row of keys. Does this appear normal? If the issue is still present here, it's a hardware issue and you should contact Apple ((46) 0771 199 519 in Sweden) for a repair.
If the issue goes away when booted to the DVD, it's a software thing. Let us know, we'll continue working with you.
Best of luck.