Comment 10 for bug 88095

I've also experienced this. If windows wasn't shut down properly and the NTFS journal is incomplete, gparted will (understandably) refuse to resize it. This therefore affects both the live cd installer and the alternative installer.

I had to run gparted by hand to find the error buried in a sub-sub-subs-sub-menu. After that I just needed to boot windows and shut it down cleanly to get everything to work. But finding the error was not trivial.