I don't use a mouse. I'm on a laptop so use this annoying little touchpad. Can't use a mouse if I wanted to (long story I won't bore y'all with).
There has to be something we're doing. I swear I just hit the down arrow after typing and just letter keys. It doesn't happen always, just intermittantly, but is annoying.
Will be back after I eat then reboot and hit F8 Safe Mode with Networking ... but this happens once in a while so rebooting won't help at this time. I'll have to wait until it happens, then F8.