I run a small website with a few users, low traffic, mostly to share personal mp3 files with a small community.

Depending on their ISP, my users can't always download or stream larger files. By larger I mean larger than 1MB. Essentially the host either stops sending, or the client stops receiving. One of the links along the connection chain simply ends its connection before the transfer completes

Trace-route shows no connection issues. There are no connection issues with short transfers that don't take more than a few seconds. It's these 10 second transfers that just end up ending.

Just doing a straight download with a direct link can yield this error if you have the wrong ISP.

Strangely enough, this is most common with users with ISPs who are essentially independent providers that buy service via a fiber link. Unfortunately these providers aren't very knowledgeable, are unable to do any testing, and insist it's a problem with the host.

I have gotten my host to transfer my site to different servers of their, to the same effect. Nearly identical sites (affiliate sites actually) experience no such issue.

What can I be doing to further troubleshoot this matter? How can I prove that someone is dropping the ball, and identify who that party is? Can I do a 5Mb traceroute?

EDIT

Maybe I can clear up some misconceptions with my question:

1. The files are not very large. They are simply over 2Mb.
2. The users do not have "slow" connections, they are at least 5mbps.
3. This "time out" happens very quickly, in the realm of 5 seconds, so I don't know if it's a timeout or not. The user often gets 1 or 2Mb in this chunk of time.
4. I have tried streaming with a flash player.
5. I have tried saving the target. Forcing the download.
6. I have tried allowing the browser to stream the file.
7. I have tried different browsers (FF, IE, Chrome).
8. Users are able to download identical files when on different hosts.