Reader X does not ship with a help function other than Internet-based help. There is a downloadable "help" PDF for reader X that can be referenced, but it is not accessed with the F1-Help function. Maybe they will fix this some day.
Is your computer behind any firewall, Such as ISA or TMG. We had a similar issue and it has got resolved by installing ISA firewall client. Since the Adobe help uses anonymous credentials to access the internet and its getting blocked by ISA servers.