Just to keep you all informed about this, in case someone run across the same issue I had. My N900 camera focus is working again. What did I do?

I considered that bug above, and assumed that the lens were stuck. So I took a deep breath and dropped my N900 at my bed, letting it hit a hard surface (i used a cell phone battery) at the lens area (the shutter was closed. I just needed the impact).
About 3 drops later, I tested the focus and it was moving again, but not enough to be normal. So I dropped it again a few more times and it's working fine now.

Thank's everyone for the insights, and sorry about my bad english.