Springsource Tool Suite unable to find sites

I'm trying to configure SpringSource Tool Suite 2.7.1.RELEASE

If I try to install a plugin, Help -> Install New Software... I get the following error, even though the URLs are correct.

Here is the error log:

On the suspicion that this could be related to a proxy, I have put in the following proxy settings:

but none of the variations that I've tried here have made a difference. Any ideas? Any workarounds?

I开发者_高级运维f there is a forum more appropriate for STS question, I'd really appreciate that info.

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Please ask a question on the STS forum: http://forum.springsource.org/forumdisplay.php?32-SpringSource-Tool-Suite

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Had a similar problem with SpringSource Tool Suite 2.9.1.RELEASE trying to install a maven m2e plugin. Turns out the latest version of AVG (2012 Free) Virus Scan was blocking the update process from being able to download/create the jars needed to run the update. Temporarily disabled virus protection and updates worked.