Go see if VLC PLAYER is out for this G4 Mac. If I recall there are some limitations on the G4 so you might even want to consider going back to what you had if it worked better.
I recently upgraded a G4 Powerbook (12") 1.33 GHZ memory 1.25GB to Mac OSX 10.5.2 (Leopard). Since then it has been impossible to play a DVD - I went to the Apple site to find a DVD player to download to no avail. I tried the DVD function on the Front row app. but all I get is a blackscreen with "DVD Loading"...and nothing happens. I run both platforms, Windows and Mac and I regret to say that my PC's are far easier to deal with than the Macs - I have also an Imac G5 - running Leopard. Can anyone help with the Powerbook Ge4 DVD situation. Does it mean that as soon as Apple comes out with a new OS one has to buy their latest machine? Thanks for any help with this.