All that jitters is not gold . . .

Question

I have dead-ended.
I recently purchased a Wacom Intuos3 tablet. When I try to use it, the cursor has a severe case of the jitters. It also randomly causes popups to appear, as if I were holding down the "control" key, even though none of the keys on the tablet or pen are set for "control". It is worst in my 3D modeling & CAD apps (the primary reason I got it), but it will still do it with only the Finder running. In CAD, it's bad enough to cause the coordinates to change at 1/16 inch resolution. The cursor is fine when the tablet is on (USB) but it is not active. It is only when I use the pen or Wacom mouse on the tablet that it occurs. My bluetooth mouse appears to have no effect on it.
The techs at Wacom have been very helpful, but they're stuck, too. They believe it is some kind of RFI, first suggesting that it was possibly too close to my display (which does not seem to be the case), and now they think it is coming from the computer itself. At this point, all they can suggest is putting a USB card in the computer. I also believe it is some kind of environmental RFI, because how I hold the pen or touch the tablet effects the severity of the jitter. I tried it on a friend's dual G5 (although hers is Intel, mine PPC) and it worked fine. And no, it's not practical to bring hers here to see if it still works.
I have the most recent driver (as does she). I have sat in the dark with everything in the room turned off. I unplugged the cordless phone. I have turned off the bluetooth and unmounted and turned off my external firewire drives. I have no wireless networking. I have had no mice or keyboards connected. I have plugged the tablet into different USB ports. The only things on in the room are the computer, the Apple cinema display and the dsl modem (about 30" away). I'm in a ranch house sitting on a concrete slab. The nearest commercial radio transmitter is about 6 miles away. Everything in the house that I can think of that could possibly cause RFI has been turned off (including two lights on dimmers at the other end of the house). I plugged it into the front port and moved the tablet 8' away from the desk and it still jitters just as much (if it were the computer causing it, the interference should have dropped by a factor of about 16). The only thing that slows it down, but doesn't eliminate it, is if I put my bare foot on the computer case - I'm assuming I'm draining some of the RFI I'm channeling to the tablet.
So . . . Does anyone know if the computer can be a source of that much RFI, or of something else in my environment that may be causing it.
Thanks.
dual 2.5 G5   Mac OS X (10.4.8)  

Answer 1

Hello, all! The saga continues . . . .
Well, I'm closer to isolating the problem from my recent machinations, but let me first address your latest round of suggestions.
Daniel:
Not ground loops. Right now, my setup is such that the recording equipment is only connected to the computer by optical cable (I/O). The computer analog out runs to an amplifier, which I had pulled. And I know people are checking in, because the "views" count keeps going up. Thanks.
japamac:
Manual-read(?) meter. No home security system. Water meter is is remote-read, but they drive by & ping it. And it is possible: I felt like I was "probed" the other night. And we refer to my next-door neighbor as "The Alien". He's OK, but he REALLY keeps to himself, and sometimes he does things that are toward the edges of the bell-curve. Whenever we have random interference on the TV, we say he's trying to contact the mothership. As for Big Brother, I'm sure I was on lists in the 60's & 70's as a "known associate". Years ago, when my sister would call, we would sometimes get strange clicks & noises on the line, so we would just start talking to the FBI agents. They might just be using more sophisticated bugs.
DaddyPaycheck:
I've tried it in the dark with everything turned off. Today, everything in the room was unplugged except the computer and display, everything was disconnected from the computer, fans & humidifier in the house turned off, fridge unplugged, etc,, and I waited until the furnace cycled off. The house was dead. It jittered.
So here's what I did (after I turned the house back on). I took things to a neighbor's a couple of doors down. Her power comes from a pole about 150' from mine, but it's about 3/4-1 mile away on the grid. That side of the neighborhood goes out about 4x more often than this side. Once last summer, they were out for about 36 hours and we flickered a couple of times. It worked fine. So maybe it's interference on the line.
I take it to the next-door neighbor's (not the Alien); the house between. The two poles are on the back corners of their property. 2 years ago when they remodeled, they had the service drop moved to "my" pole, and have missed out on maybe half a dozen power outages. I set it up and . . . . it works fine. It's not line interference.
{SIDEBAR: The neighbor was quite impressed with the Mac (she runs her medical transcription service over the internet), is now quite unenchanted with Dell, and will probably be converted before the year is out.}
I lug the stuff home and set it up in the workshop, the farthest place in the house away from "the office" (and not really a healthy environment for a computer). The jitter is slight, but it's there. I move the rig to this end of the house, but set up in the hall down from the office. More jitter. I set it back up, reconnect everything, do a little troubleshooting . . . St. Vitus' Dance. It's the room. (And yes, it is the end of the house near the Alien's)
I pondered a bit and came up with a plausible, yet bizarre, reason for the interference. I'm going to play this one close to the vest, because it will take me awhile to set things up to test my thesis. Hopefully tomorrow.
So, thanks again to everyone, and I'm still entertaining suggestions. I could very well be dead wrong again.
dual 2.5 G5   Mac OS X (10.4.8)