I've just checked my whole collection and came to his conclusion:
A movie with () at the end will not be recognized. Remove it and it will.
Just enter the name in Boxee without the () and it will be recognized 95% of the time.
A movie with : in it's name can cause the same problem.
A non-english film with an English title will not be recognized. Boxee will give you 90% of the time the real film name as an option though.
What I would like to see is an option to use the English name. I have a lot of Japanese and Italian films. I know them by their English name and not by their original name. Now where's Ghost In The Shell (the anime) gone to?
Even better would be if Boxee would display the different titles under info and that you could specify an order to display the titles in. This would be very handy for all the Spanish, French, German, Dutch users out there once Boxee gets out of alpha.