Java and choppy video playback

I am currently the owner of a 1 GHz G4 iBook and I was wondering if any of you are having video playback problems when running Java apps like Limewire or Azureus. Specifically, whenever I playback a video that's encoded at a bitrate higher than 512 kb/s, the video will often jump/skip around, and it is maddening when this happening. This only occurs when I am running Java apps (mostly P2P clients), and when I run native OS X applications like iTunes or am browsing an iPhoto library, video playback seems to go on rather smooth. I try not to push my notebook too hard when playing back video, as I'll have just 1 or 2 videos downloading and then I'll run Quicktime in the foreground. Even though hiding other apps will help out a little, I still find that my video will studder, and it's quite irritating to see this sort of thing happen. This is the one area where I feel somewhat let down because Apple is supposed to pride itself on it's ability to create and playback a variety of video content and I just can't see why my G4 "supercomputer" processor can't keep up with this sort of thing. I honestly feel it's not a hard drive issue because when I look at processor usage when playing back a video, it's often above 90% and the skipping seems to occur whenever the processor can't handle the demand and it'll choke once it hits that 100% threshold. I do the same sort of thing with my Athlon XP 1800+ (w/ 512 MB Ram), and quite often I will be running Eclipse, Limewire, Azureus, iTunes, and maybe 2 or 3 SSH clients in the background, and playing back movies in VLC player is not a problem. So I was wondering if it's just me, or maybe there's some setting I need to tweak in either Java or OS X to be able to make things work correctly. (I always run my iBook at Highest processor speed in the Energy Saver preference pane by the way.) Thanks.