Could anybody help me with the IIS VOD problem: "Streaming Error: Reached the end of known chunk list with 8 consecutive chunk errors. Buffer cannot progress;"?

hi,

I made ismv/ism/ismc files with my encoder,  then upload them to IIS server (IIS7 / IIS meida service 4 sp1), and try to play this file by silverlight, but there is no audio and video, the player give me an error message:"Streaming Error: Reached the end of known chunk list with 8 consecutive chunk errors. Buffer cannot progress". 
I know there must be some  format error with my file, but i can't find where the errors are.
Could anybody help me with this, thanks very much.