What is the craziest symptom a dusty computer mouse has displayed?

Personally, aside from just not working, I haven’t ever had a mouse go haywire.

By itself, a mouse only really controls the location of the pointer, whether it clicks or drags with one or more of it’s three buttons (most mice have two buttons and use the scrollwheel as a middle button) and whatever function is assigned to the scrollwheel, which is usually just scrolling. I say “usually” because some programs because some programs use the scrollwheel for something else; zoom in/out in some graphics programs, select inventory items in certain games, etcetera.

I’m not sure how old your computer is, so I’m mentioning the old ball-mice as they were quite problematic. Older mice had balls that would collect cruft and eventually have serious issues moving the pointer until you clean the ball. I generally considered myself lucky if I could go two weeks without a ball cleaning. But >99% of mice today are optical; they don’t collect crap nearly as much, and if they do get dirty, a quick puff of air or swipe with a Q-tip restores them to normal function.

The mouse really can’t do anything truly crazy without help though, and the most likely thing is for it to just respond intermittently or not at all. Any problems not listed thusfar are problems beyond the mouse.

Holding the Ctrl key and using the scrollwheel in a browser is the command to change font size, and I would consider that to be “crazy”. But if it does that without you wanting it to, that is an issue with your keyboard, operating system (a driver issue) or possibly even your motherboard (specifically, the chipset controlling the mouse and keyboard) rather than your mouse. I mention this one specifically because I’ve had a stuck Ctrl key before and it caught me off guard, and realistically, the keyboard is the most likely fault, and is also a common one as keyboards do wear out, get filled with crumbs, get dripped on and otherwise age ungracefully.

Usually the first step to nailing these issues down is just swapping out the keyboard and mouse to see if that really is the problem, or whether it’s something else. A new set can be as low as $15 even for brand-name replacements that are often higher quality than the original equipment. (I don’t use the set that came with my computer, so I have “known good” spares for testing.)

I don’t know if it can be directly attributed to the mouse but one time my curser used to slowly move across the screen on its own. Changing the batteries out on the mouse made it stop.

Lots of laser mice do this. Try switching the surface that it is on.

If that doesnt work theres not much left but the drivers failing..

Thanks all. I didn’t experience it though.

I’ve only seen pointer movement weirdness. If hair or fur or lint goes up the tube of an optical mouse, it can make the cursor move in weird ways, sort of wandering jerkily around by itself. When trying to use it, this can result on doing something unintended, depending on what software and OS is running.

Dust and crud accumulation on physical ball mice would tend to make them less responsive, and add a little bit of jiggle/warping to the course, but not add movements.

Crud in a keyboard can result in some bad things happening, particularly if your Shift, Alt, Control, Fn, etc keys get stuck down. This has fooled me a few times into thinking my OS and/or mouse were broken, because it can change what most/all mouse clicks do or don’t do in many programs / OS’s.

Oh, and touchpads can be crazy-making, especially on laptops where the hands can swipe against them when using the keyboard, and especially when they combine click and wheel / swipe actions into a smooth “buttonless” design, meaning it’s even easier to accidentally do bizarre things beyond just moving the cursor. I disabled mine due to this.

True, @Zaku, While I loved my trackball, I had to clean the optics out quite frequently. The grime from my hands would cover the ball which would then scrape itself off at the holes. I do miss my trackball however.