I experienced a few 'freezes' on finale 2014.5 a few months ago. Most commonly, I could not change the time signature. This has progressed exponentially over the past few weeks. Now I cannot input notes on the programme or select measures. It is actually useless. I have neither changed nor updated my mac software during this time. I am on Yosemite 10.10.5
If anyone can help I would be very glad. I was a Sibelius user for 10 years and never experienced anything but the occasional freeze.