After you install a very old version of the SourceGear Vault client (v220.127.116.1198), opening a link in a new tab in IE 9 will hang that new tab. This is caused by the SourceGear Vault isntaller, overwriting some registry settings. I posted a similar problem on IE 8 [https://www.roelvanlisdonk.nl/?p=871], but that fix, did not fix the problem in IE 9.
I found my solution on: http://iefaq.info/index.php?action=artikel&;cat=42&id=133&artlang=en
Running the [ie8-rereg.all] fixed my problem.