BlueMooner: www.desura.com
Is it just me?
EDIT
Apparently it's a US thing. I'm sure it'll be fine eventually. Thanks for checking guys.
EDIT 2
Apparently it's a bluemooner and pimpmonkey thing. I'm guessing Desura was suffering from sexy overload, so they had to block the major offenders before their servers blew. Once their servers have recovered, I"m sure things will be fine. Clearly we should use more lube in the future.
Both Desura and IndieRoyale have been inaccessible to me over IPv6 for several months now, and since I'm dual-stacked my applications prefer IPv6 to IPv4 when both are available. As a result by default I can't access anything on their websites, nor does the client work. In Mozilla Firefox I overrode this using a hidden config setting (ipv4onlydomains) to force desura web properties to be IPv4 only and got the website back up, and did the same for IndieRoyale, but to date they're both inaccessible over IPv6 so anyone who is using a dual-stacked host may have a similar problem.
I contacted Desura support to report the problem and I received back an email from one of their people saying that they are aware of the problem for some time now but have not been able to figure it out yet, and asking for me to do a network dump and some diagnosis to help them sort it out. I just haven't had the time to investigate it further, but plan to eventually when I have the time and inclination (low priority for me ATM). The way the problem manifests itself is pretty much symptomatic of a classic broken PMTUD setup somewhere along the network.
Dunno if you might be having the same problem or not, but others are likely to be increasingly as IPv6 spreads so sooner or later a large number of people will be impacted I imagine unless they sort it out. :)
In the mean time since there's no easy way I can tell to force the client to be IPv4-only, I stopped using Desura until I have the time to diagnose further or they manage to sort it out on their own. If I had to put my money on the cause of the problem, I'd bet that their firewall or their upstream's firewall is blocking ICMPv6 outright in violation of RFC4890, which seems a popular thing to break these days. :)