Help!

Our office has a small network of about a dozen PCs, connected via a router to a 2Mb/512k ADSL connection.

Everything is fine...... until someone uploads data. The connection that's sending data out to the net grabs all the bandwidth. Nothing else gets in or out. An http upload is bad, an ftp upload is much worse. I did a test: pinging one of our off site servers, normal round trip is about 60ms. When doing an http upload the same round trip goes to about 220ms. When doing an ftp upload the round trip hits 700ms!!

I'm very confused. I've got ADSL at home as well - uploading files there is no problem, doesn't swamp the connection or interfere with other regular traffic.

What's going on???