I don't think that the voice thing is an actual slip-up. Computers now pretty much sound the same when they talk. Talking with a computer might have been newer technology without alot of development into various voice ranges. And as for speaking while he typed? Some people do that to remember what they want to type, and it was intentional so those with bad eyes could see (I mean hear.) what he was typing.
Don'cha just hate when you're old enough to remember when every single speech synthesizer sounded exactly alike?
Bout the time the movie came out, yep, they all did. As for a talking computer in Norad? Well, heck, apparently the whole thing was just a marvelous replacement for the dead son of it's creator, right? So who wouldn't want their child to talk?
Get the DVD release and listen to the commentary. They knew this was a potential problem when they did it and just decided it helped the story flow. I guess that would be an "intentional slip-up" if there can be such a thing.
Good one! I thought the same thing when I saw it.
Also note: (Since I'm too lazy to start my own thread) That in the movie they start with DEFCON4 and 'upgrade' to DEFCON1. In actuality, DEFCON1 is peacetime, and DEFCON4 is wartime.