Classic British Flight Sim

Just tried to fire up FS9 on the main PC not used it for ages, shut down soon after opening screen with message of exception..error... etc etc All I got to was the scenery cfg updating, the fs9.cfg picking up two old modules, which oddly were listed in "old modules" section of cfg. After that it goes to small splash screen then a windowed small screen with the menu top bar of fs9 then shuts down.
Now I always run in full screen, I have removed the cfg and tried to let it build a new one but it doesnt get that far... I uninstalled the update and also the fs9.1 exe file then re installed all with no luck.... Hoping its another easy fix ... Any ideas guys??
Cheers Tony

I decided to do check many thanings
Video drivers
Defrag
FS9 Register Repair
undo FS9.1 update and re install update
Replace FS9.exe
All with no luck
I then copied my FS9 into another folder and reinstalled FS9
It failed to start when installed....I then sat back and looked for something different and found what I hope is the answer.... Webroot Firewall.....It was installed with the Webroot software on an upgrade and is so bloody fussy. So I went into settings and allowed FS9. The new installation ran perfectly.
So I started copying folders from the back up FS9 and all worked well.
So I renamed the new installation to xxfs9 and put my original back into operation and again it worked. I can assume that the firewall was the culprit. Odd though as it normally gives a warning if it is blocking. Time will see if this was a fluke or the real problem.
But at least I have a spare FS9 if required