UAC and securtiy settings, even though it may be in your trusted sites, for IE the actual program could be stopping it from running because your security is to high. You may need to save what is being blocked to your hard drive and then install it, 7 does not allow you to save to some areas directly from the net.
The way I got it to work was to go in an disable all the different internet security setttings, I couldn't even use youtube before this. Now all is fine but I feel I have xP security. There should be a guide as to what enable, prompt, and disable.