I had issues with the installation also (have done for the last couple of releases). For me, seems to be a problem when installing from a limited account (although prompted for administrator account). After installation finished, running under limited account doesn't work.
Last time, logging on as administrator and then running IceDragon corrected the problem for the limited account. This time, that didn't work so had to manually download IceDragon and run directly from administrator account. Next time, I'll create a bug report should it happen again.
