I've run into this a number of times when trying to open prior years' programs. Rebooting helps sometimes but not always.
I did have this happen once with this year's program a few weeks ago. Rebooting didn't help. I ended up doing a system restore, and that resolved the problem. I believe an anti-virus (not anti-virus itself, but related security; I use Norton) software update was the culprit, but I'm not sure.
I hope this helps.