A friend of Mine (Katana) removed a mouse from a computer while it was running and since then the computer will turn on but no mouse can be used in it

Has this been noticed before?

-pi

lesson learned the hard way.
unless the device is connected with a usb connector you never connect or disconnect a device with the computer on

there are two notable exceptions to the rule:
you can connect/disconnect your monitor
and you can connect/disconnect a serial mouse

other exceptions are:
external sound card connections
external modem connections

It was a USB mouse

Did she unplug it cleanly or while doing so, did she keep it stuck around the socket rubbing against it? I've accidentally unplugged something while on and it rubbed up against the socket and created a huge ass spark and fried the port, heh. Needless to say, I make sure I do a quick and clean unplug now.

- N

With USB, when you plug something like a Mouse in (or web camera/printer) the operating system will usually automatically sort out the drivers and reference which port the hardware should use. On unplugging something like a Mouse from USB the operating system doesn't necessarily clean up it's driver settings, which means if you decide to plug the mouse into a different USB port than the one it was configured on it won't showup or work.

Try plugging the mouse into a different USB port.