[Using Sakai] lessonbuilder cannot play flash online?

[wendy lee]

hi, all

I add a flv file into course resourses. The file can be downloaded and play correctly. 
Then I use Add Multimedia to add it. When trying to play online, it reports "We are unable to connect to the content you've requested. We apologize for the inconvenience".
Lessonbuilder installation uses default setting. It can play .mov file online. Should I set something for flv? THX 

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 wendy