Had this one a few months ago, while making a huge order, changing a few details, and asking for the new grand total.
The thing is, I've got a screen with very high resolution(3200*1800), and W8 runs in double size for the letters to be readable. I assumed it was the cause, and didn't pay more attention. Schro, do you have a similar configuration?
Anyways, I made a few tests with E145, and it seems that what breaks the display is adding new types of planes. I had only ERJ145LR at first, but when I added more variants & clicked "calculate again", the variants summary was the part overlapping the "detail" lower part. If I stick to one single variant, the problem seems not to appear. Changing just the payment does not cause the problem either.