AirTunes connects on PowerMac, NOT on WindowsXP!

Question

I am an advanced computer user, very knowledgeable with everything technical, yet I am completely lost as to what is happening.
AirPort utility locates the base station just fine,
the base station is connected to my wireless network,
iTunes finds the base station and offers me to connect to it,
a macintosh computer connected to my wireless network will connect through iTunes no problem,
BUT
on all windows XP machines the connection through iTunes times out. I get no error messages, simply a 'connecting to stereo' message for 30 seconds which then disappears.
Odd things:
1)at first, iTunes on windows XP would not connected through airTunes on any computers. An hour of fiddling through options later, it worked on ALL of them. It worked for perhaps two hours, and then would randomly stop and start. By the end of the day, it worked NOWHERE, and since then has not worked at all. (It's been 4 days since then of complete confusion on my part, since I HAD IT WORKING FOR A COUPLE HOURS!) I tweaked setting after setting, and each time the Macintosh would happily connect, while windows XP did nothing. I'm a computer programmer by profession and this has me baffled.
2)when I have the airport utility installed, my windows zero configuration (the default wireless utility with XP) will randomly disconnect from my router. Not only that, but sometimes it SHOWS ME as disconnected, ("not connected") but IS IN FACT connected, as I can browse the net, chat on AIM, etc. Then 10 minutes later it will disconnect again. I can't go more than 10 minutes connected before it disconnects again, and connecting back is seemingly RANDOM. I have NEVER in my life seen something so bizarre. (Another thing I just noticed: my WEP password actually gets DELETED or CHANGED from saved memory, and the checkbox that says 'the key is provided for me automatically' magically gets checked sometimes. To connect I have to go in and RE-ENTER my wep key. )
Please, I am going crazy. Does anyone know what is going on????? ANY insight will help. When you suggest fixes, keep in mind that it was working at one point on all computers - so things such as 'open your firewall ports' are not relevant.
Thank you

Answer 1

Yep.
Put the G5 to sleep one night, wouldn't wake from sleep --still under Apple care, long story short, longer phone calls w/ Apple tech, but they had to come out and the last thing the guy tried and replaced was the power button (funny when he was taking it apart, I held the button and said this sounds loose, but he said, well if it was faulty you'd see this and that -- turned out your truly was right) and that turned out to be it an only it. Replaced, been fine since.
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