UDP file upload killing other traffic on SonicWall

So we just started using Signiant Media Shuttle to upload media to a remote site. It uses UDP to maximize the upload speeds. The problem is that when Media Shuttle is uploading a file, all other traffic is slowed to a crawl. Media shuttle is capped around 90mbps, but our total upload capacity should be around 500mbps. We should have plenty of bandwidth to do other things, but even accessing web pages becomes very slow. We ran into this with another similar piece of software, but the client allowed me to set limits on bandwidth, and only caused problems when the limit was set to "max", which I assume basically told the software to push the packets regardless of other traffic. Media Shuttle does not have options to control bandwidth on the client side. I've tried setting the priority of traffic on those ports to low, but it does not seem to make a difference. Any ideas?