For months the iPad 2 remained pretty much untethered jailbreak proof. Then last week a PDF exploit to jailbreak it went public. Apple is now pushing an update with just one feature "fixes malicious PDF exploit".
Probably want to avoid that update for now if you want to jailbreak or keep a jailbreak.
http://arstechnica.com/apple/news/2011/07/ios-434-closes-pdf-vulnerability-that-enabled-untethered-jailbreaks.ars


