Are you getting the message “Internal PortAudio error. No Devices Useable” ? When audacity first starts up it scans all of your audio devices. Perhaps there is another device in your system that is causing the Audacity to choke. I wonder if “Disabling” each of your audio devices would allow Audacity to start up. If so, it might be a simple matter to find out which one is causing the problem. See also Internal PortAudio error. No Devices Useable.
If the error is on a specific device, try changing your Host selection. I hope this helps. 