Hello,
A few days ago, Hugin displayed a dialog stating that it could not find an entry point (sorry, I did not write the entry point name, I can't remember what it was) and that it was disabling Fast preview. AFAIK, there was no recent Windows update, but I hadn't used Hugin for a few weeks, so I don't know if it has a relation with a Windows update. I was using Hugin on battery and I use a tool which automatically disables some Windows features when running on battery, so maybe this automatic disabling interfered with OpenGL. Also, I had a dozen Hugin simultaneous sessions and it is possible that some of those sessions were in Fast preview, but several sessions displayed the dialog at the same time.
I did not worry too much about it, I thought I would re-enable it in the settings. I reloaded Hugin but I was unable to find how to re-enable the Fast preview. Fast preview seems to work perfectly in 2012.0.0.
I am using Windows 7 64 bits.