I have precisely this problem and it is, at times, freezing so frequently as to be utterly ridulous. Sometimes I can work away for quite a while before it starts but when it does it will freeze the screen, sometimes for a minute or two, just at the touch of one key. A simple operation like shifting from 'people' to 'plan' view will trigger a freeze, the screen will fade, and a message appears in the top left of the Windows screen saying 'not responding'. I had none of these problems with FTM 2011 and this problem is making the 2012 version almost unusable at times.
I emailed customer support about a week ago but did not even receive a response. I love the features of FTM and upgraded to 2012 mainly for its better handling of blended families, of which I have many. My trees are quite small so this is not an issue and the problem does sometimes seem to be better if I work 'offline' but, for me, this defeats the purpose as I do a lot of searching and merging with Ancestry within the software and, again, this is a feature of FTM that I like over and above the competition. Even so, so frustrating have these experiences with FTM 2012 been (I have also had the Sync problems, though no so bad) that I have been trialing other software. I don't want to jump ship or go back to FTM 2011 but it may be I have no other option unless someone has a clue just what is going wrong here? I have only been using FTM 2012 a month or so and it has the latest updates, etc.
Before someone suggest it yes (as above) I have tried working whilst disconnected from Ancestery and offline and it is better but does still freeze on occasion. Moreover this is not a solution it is simply avoiding the problem since the web intergration is a significant feature of FTM for me.