OK, the following will work but I'd give up the idea of having a Movies folder in a normal user account being shared. However, I can't see this giving issues and it does work in FrontRow.
Open Finder and navigate to the /Users/Shared folder
Create a new folder (for example, "My Shared Movies") and then create an Alias to this folder
Copy the Alias to the Movies folder of each user account you wish to have shared access to the movies (you can rename the Alias as well)
Copy the movies that you want to share into the folder you created under the Shared user account
Each user will now have access to the movies in FrontRow by selecting Videos > Movies > "Name of Alias". Pretty simple and it does work.
Great, thanks. What I did was open up my Movies folder for read permissions, and created a symbolic link to it from the users account, in their Movies folder.
I can't say that I'd advocate mucking around with the permissions of key folders in your home directory (or elsewhere for that matter) but if it works for you then that's OK. Regardless, the basic principle of this solution works and that's the main thing.