Found the answer from another forum:
"Confirmed: I experieced exactly the same problem with 1.5.0_05. Rolling back to 1.4.2_05 fixed the problem, but the app I was using needed the later runtime. Only after uninstalling IPV6 by using the "netsh interface ipv6 uninstall" command was 1.5.0_05 restored to it's former glory.
For those interested, I am pretty sure this co-incided with the installation of Microsoft Codename Max, which is based on WinFX and turns on IPV6 by default (it actually needs it). Shame, because Max was kinda cool."