µTorrent blocks internet traffic

[ccMatrix]

I have a bad problem since switching to µTorrent 1.8. Running µTorrent blocks all other internet traffic: Miranda disconnects from ICQ/MSN/Jabber, Timeouts in Firefox. This doesn't just affect my own machine where µTorrent is running but also any other machine in the LAN. It even affects http traffic to other local pcs and the router.

I am running Windows Vista Business 64bit with 4GB Ram.

My internet connection has 2048kbit up and 160kbit down.

tcpip.sys is not patched - µTorrent 1.7.7 doesn't give the symptoms so I didn't think this would be necessary.

I have set the maximum Upload rate in µTorrent to 6kB/s. The maximum number of connections is currently set to 100 and the maximum connections per Torrent is set to 25 with 1 upload slot per torrent.

I tried disabling UPnP and NAT-PMP port mapping with no effect. I also tried to lower the number of maximum active torrents from 4 to 2 with no effect. At the moment I have just 1 active torrent and the issue.

I have the WebUI active but disabling also doesn't affect the issue.

I have set net.max_halfopen to 4 down from 8 but this has no effect. peer.resolve_country is disabled. Access to DHT and external access is working when UPnP port forwarding is enabled (I get the green ok sign in the status bar).

Download speeds are fine so the problem doesn't seem to affect µTorrent itself.

The problem affects the whole LAN after µTorrent is running for a few minutes but stops immediately after µTorrent is closed.

If any more information is required let me know. I also tried to run the latest 1.9 but the problem is there too. So it must be something that was changed or added in 1.8.

[thelittlefire]

And if you disable DHT PEX and LPD?

[DreadWingKnight]

What internet security software do you have installed?

http://forum.utorrent.com/viewtopic.php?id=15992

[ccMatrix]

I disabled DHT, PEX and LDP. When I re-enable DHT the symptoms returned. Seems like it is connected with DHT. At the moment I am running with LDP and PEX enabled. Weird how I forgot these options when going through the options.

I'm running the Windows Vista Firewall and Avira AntiVirus Personal as a Virus scanner.

Any reason why DHT blocks internet traffic in >= 1.8 but not in 1.7 ?