[Swampdude]

Sounds like some sort of right clicking gone bad combined with a mouse control issue. In AutoCAD you can modify the way right clicking works. Either it can be a return, a last command prompt or a shortcut menu. It also has a timed response feature if you set that stuff up. Being a public machine, it wouldn't be hard to go into your mouse hardware settings and create some software setting conflicts that would do a number on AutoCAD's right click options. So I'm guessing your problem would happen only while your mouse was in motion, telling AutoCAD the right click feature was in use. Hence activating a constant "return/enter" thereby running every kestroke immediately. Probably had your command line scrolling the commands over and over as well?
Just a guess, otherwise it's like Al said, just some kind of glich wreaking havoc on the "return/enter" response. I think the fix would be found in your mouse settings/driver setup etc. But like someone said above, a reboot can cure 90% of AutoCAD's ails. Which might have put the settings back the way they would normally initialize.