transmission errors

I have only been using transmission for a short while, but have two Qs:

1. on a couple of recent torrent d/loads, they have not even started, and carry the error/caution yellow triangle w/exclaimation mark, followed by message 'tracker returned 4xx message'. Anyone know what this means and how to get the downloads to start?

2. after checking on speedtest.net my u/l and d/l speeds, it is showing 2172kb/s UL and 412kb/s DL speed. However, using transmission, my d/loads still seem very slow. I have used port forwarding,and although better, still not what I would expect in terms of D/L speed. Any suggestions on ways to improve further?

Thanks.....

BitTorrent is a P2P technology, which means you can only download as fast as other people are uploading the content to you. The more people there are who have the file (or at least large parts of it), then the quicker you'll get it all (as a general rule; there are other factors too).

As for the tracker message I'm not sure, but not all trackers allow every client. See if you can get the same content from a different source.