Very weird 888/24 MIX random output volume change

[chroma17]

Hello,
I am posting this on behalf of a friend whose studio I am working at. They have a MIX system with 3 888/24's. Running off a G4 Quicksilver with 1Gb of RAM, currently 10.3.9 and Pt 6.4.1. Within the past month or so, they have been having a problem where the volume of one or two outputs of the 888s will randomly change by 10dB or more. The fader value and output meter in the PT mixer will stay the same, but the volume coming out of the 888 will change suddenly, either getting way quieter or way louder. For example, a guitar track may be peaking around -6 on the internal mixer and the 888 meter, but then suddenly it will be slamming all the way into the red on the 888 meter (and coming out of the 888 much louder) but still be showing a peak of -6dB in the PT mixer. The fader in the Pro tools mixer doesn't move so it's not an automation issue. Usually this happens to two channels at a time, but it could be any of the 24 outputs. The internal system drive was completely erased and reformatted, the PRAM/NVRAM etc. were zapped, OS X 10.3.9 was reinstalled and PT 6.4.1 was freshly installed. There are no plug ins being used. All cards were reseated, all cables were disconnected and reconnected. Never even heard of this problem before and I have been using PT for ten years! The studio owner tried to call Digi tech support and was basically laughed at for not upgrading to HD (which they can't afford)

Any ideas? Anyone have this problem? Sounds like bad hardware I guess...could it be bad RAM?

Chris