stream flv from fms

I am on a 1.5mb connection with a 7mb flv file on the fms server and the stream is awful. stop start stutter stutter.
It really is un-watchable.

If i set flvPlayBack isLive to "true" then the flv want load. It will only load if isLive is set to false witch contradicts what the doc's say.

I tried to increase the bufferTime to see if that would help but with no joy.

any help or advice very much appreciated

thanks
Paul