Comment 265 for bug 417757

As you have both a working and a not working configuration, this makes you the perfect candidate for giving more details on that problem. Please give more details: What *exactly* is the problem you are talking about?

Is it a problem while resolving a name to an IP address? (DNS)
Is it a problem connecting to the other host? (Syn, Ack, etc.)
Or is it a problem while beeing connected in some kind of TCP session? (bandwidth, etc.)

If you are not sure, please use wireshark to monitor your connection. (All phases above are visible there and their timing.)
Please do so on the "working" and "not working" system and report the difference.

But since you are pretty sure it has *nothing* to do with IPv6, it is almost certainly another bug.
So *please* open a new bug and give only a pointer to the new bug here.

Hopefully this will finally bring some light on the cause of that issue. :)