Progressive 25P problems.
I just had this same problem, and after many pulled hairs,
someone within these forums was kind enough to help me, so here's
his same response for you:
A couple of things to check:
If you are getting the can't find file issue while in the
Flash development environment, I found that placing the file on the
server, and then trying to view the file separately through its own
URL in Internet Explorer on the machine you're developing on for
some reason allows the Flash IDE to find the file. I guess it must
be in some interdependent with Internet Explorer..
If you can't access the file separately from its own URL then
its possible your web server hasn't had the MIME type for .FLV set
up, and doesnt allow it to be served. You can check this by
reviewing the MIME settings:
In my case, it was definitely a case of the server needing to
be updated - if you don't have access, you'll probably need to
contact tech support, but it literally was a couple of very quick
steps for our IT tech to make the update...
Hope that helps - thank someone named "nick" for this tip,
I'm just "paying it forward..."