Funny, I have the exact same problem as you crash. My site is a custom size @ 864px and all of the bleedin' horizontal nav bars stop at 760(ish) or shoot up to 851.6px wide. None of them will size correctly . I've tried to uncheck "Adjust button widths to labels" but the result is even worse as the buttons are all the same size with text that crowds over other buttons... Im sure this is supposed to happen but I am clueless what to do to make the buttons size correctly again. It's a sad loop I am stuck in and I'm sure not the last one.