Silverfast Sucks

I know I'm trying to scan negative films, which most scanners / software aren't too happy doing from time to time. But why does Silverfast keep producing blue scans? I've set the guide markers, I've told it that the film is a negative film, I've chosen Kodak Portra from the Negafix window, and still... it gives me a blue scan. But only sometimes, and when it diverts to giving me a blue scan, the only way to stop it from doing it is to tell it the film is a positive, revert back to negative, go through the whole preview scan and then touch wood, it might, just might give me a non-blue scan. I should also point out that the preview screen gets it right every time. I have a nice preview with good positive colours, and a crappy blue scan for my troubles.

Why is some scanning software so flaky? You shouldn't have to do certain things in a certain order to make things work. The software should *stop* you from doing the wrong things and take care of the other stuff.