My wife and I both have wireless keyboards and mice on our PCs which are in the same room. Both are Logitech. Mine is a set. Char’s mouse died, so she has the keyboard from an identical set, plus a separate Logitech wireless mouse with it’s own mini usb receiving device. This new mouse does NOT have a sync button like mine does. We’ve had this setup for over a year with no problems.
Today for no apparent reason, my mouse is suddenly moving her computer’s cursor. Her mouse does not affect mine at all. We haven’t changed anything. We’ve tried everything we can think of to stop this from happening, but no luck. Any ideas?
I battle wireless mice every day. They get into the garage and make a real mess in my storage boxes. If they were the wired kind, I’d just cut their cords. But these guys are much trickier to catch. Especially the big ones.
I would so mess with my own wife and if we had two computers, I’d start making her computer seem possessed. That would be the most logical conclusion to her.
Anticoagulants?
Who am I to give technical advice, but what are you feeding the mice and have you changed the feed lately? Take out the mice batteries and re-install them. Is there a reset button on the bottom of the mice. Try interchanging the USB receivers. Try a different USB plug. Try using different rooms. I didn’t mention “cheese”, Paul. Mice like cheese.
With regard to wireless mice in the garage, when they started chewing up things in the trunk of my car, I had to take drastic action, resulting in the sudden death of four mice, I’m sorry to say. I also laid out $25 for a steel garbage can to store my bird feed.
Darn. I thought it was going to be participatory entertainment, like Robot Wars.
In case anyone else has this issue, the fix was to reconnect my mouse.
Hold the connect button on the receiver for 20 sec. This disconnects the mouse (and wireless keyboard too).
Press the connect button on the receiver once, then press the connect buttons on the mouse and keyboard. There are apparently thousands of channels, and reconnecting picks a new one.
Still no idea why this problem suddenly appeared.
I was going to suggest that, but you said you tried
everything you could think of, and I assumed this
would be the first thing you’d think of.
so much for that assumption…
You know what happens when you assume…
yup, I’d made the same one 
maybe her batteries are getting dodgy
her receiver lost contact with her mouse, found your mouse
you took yours off line, hers lost contact with your mouse and found her mouse
you reconnected with your mouse
or Aliens 
Yup-- I did try pushing the buttons, but didn’t know about the 20 holding thing.
The battery idea makes sense, but all batteries in both mice seem fine. Previously, we’ve each changed batteries independently and never had this problem. Go figure.