SH SP problem...
 

I cant restart the first mission from the Briefing room. It loads all the way up and I can watch the intro movie but as soon as the map finishes loading it kicks me to the Continue screen. Quick Saves work fine but Im currently playing on the hardest setting and wanted to try it on medium.

Any ideas?
(yes this is retail)

Remove all the custom maps/mods that you have from MOH\Main & mainta, and try again.