Another possibility: If you don't have the flash plugin, or you have an 
earlier version of the plugin, you might get a blank screen.

> I had this problem when the server I was uploading to did not support 
the 
m> ime type

> 
>>  Have you tried making a preloader?  In other words, something (created 
i> n 
>>  a separate scene) which will play while the movie is loading?
>>  
>>  Otherwise, have you tried asking Flash to simulate loading the movie 
o> ver 
>>  various connections?
>>  
>>  To do this, assuming you're on a PC, do [Ctrl]+[Enter] from the work 
>>  area.  Once the movie is running inside Flash, choose your speed from 
>>  the "Debug" dropdown menu.  Then do View > Show Streaming.  This will 
>>  simulate loading the movie over the desired connection.
>>  
>>  Your movie probably takes a while over 56k modem when it loads almost 
>>  instantly on your machine.
>>  
>>  Try streamlining things like movie clips, and removing stuff that is 
no 
>>  longer being used, like extra frames, buttons, library items, etc.