Try an earlier patch - like 1.1 or sth. Try if that works better.

Might just be a borked-up copy, in which case you should ask Blizzard for replacement.

Then forget it. I've already went past that mission. As long as it won't happen again, everything will be fine. Thanks! :)

I've been playing StarCraft for a very long time and never something like this happened to me.

If problems endure, reinstall. Shouldn't take too much time. If worry about your campaign progress, make a copy of your SAVE-folder. But be reminded taht you can skip the first Terran mission anyway ...

Did it already, but didn't work.

I know. I used a save file from dlh.net, and jumped over that mission. Thanks anyway for trying to help me guys!