My computer does the very same thing...
was beginning to think I was alone

I have very similar system to yours too.

Athlon XP x64 3000+ CPU
1Gb RAM
200Gb Seagate HDD
nVidia 7800GTX Video card with 78.01 drivers
Windows XP Pro + SP2
Latest Limewire
Latest Java VM from SUN

I see Limewire taking 80 - 99% of CPU, with javaw.exe taking the remainder.

I also notice the same with another java program, but I cant remember what it was now.

I am a computer technician by profession, and I have taken all the usual steps to work out the fault. It would appear that its caused by the java VM, except that Azureus works on my system, wich is a java Bittorrent client.

EDIT: Remembered what the other program was... its the video player at the website http://www.bigad.com.au,
which is also java based.