Tracker sending invalid data.

I recently received a new modem from my ISP, the newest model. I'm using utorrent 1.7.7 and on most of my torrents this is the error that I get: Tracker sending invalid data: <NULL>.

It is not doing this on all of my active torrents but on 90% of them. I don't know what the problem is. If anyone has an idea, your input is welcome.

Could it be because of an IP change caused by switching to a new modem?

Thank you all for taking you time to read my plea.


EDIT:
I think I have figured it out. It was probably the port forwarding. I when to www.portforward.com to solve the problem and it seems to be working. My new modem comes with a built in network. Which means, I don't need my router anymore.

Try to remove the torrents from your client and then re-download the torrent file again, then add it to the client again and see what happens. You can also try Azureus 3.