You sure about that? I'm not aware of any cameras that record H.264 to an AVI file. It's about 90% MP4 and maybe 10% QuickTime.
That suggests you're not playing with camera original media here, but something that's been converted. If so, you may want to get your hands on the originals.
It is the original data from the camera, thats what I find confusing about the whole situation.
I am really thankful for your help, but somehow I can't understand why a professional tool like Premiere can't handle H.264 in an .avi wrapper.
There must be another way for a windows pc to get it to work, even if the converting is an option.
As I said before, I tested it on a mac with Premiere CS 6 and it imports like a charm.