I didn't find anyone to help me with this very annoying problem, however I found the solution quite by accident and thought I would share it just in case anyone else gets it.
I had trouble trying to load "Just Flights 2005 Traffic" software. I was getting error message -5001. To cure this I went to their website
www.justflight.com and downloaded a small piece of software called "ISClear tool." This eliminates an "InstallShield 7 runtime error" file that can be left on your PC from previous downloads. Having removed this error file I could then install Traffic 2005. The best thing of all though was that the "freeze up" problem I was having when trying to host an on-line session in FSX disappeared.
Thought this info might prove handy for someone.
Brian