[Ti] shrinking screen - os x update

[thor]

Hi list.

I just updated OS X to 10.4.6 and I notised when restarting (when the  
screen is blue)
that there was a ~ 3mm gap at the top of the screen where a black  
stripe appeared.

Then the menu bar appeared and it is now ~3 mm down from what I am  
used to.

Has anyone else experienced this? Any suggestions of how to reclaim  
old territory?

This is on 15" TiBook 1GHz PowerPC.

cheers
thor