I changed this key to 1 and it is fixed.
HKCU\Software\Adobe\Adobe Acrobat\7.0\Originals\bBrowserIntegration
http://kb2.adobe.com/cps/406/kb406119.html
macbook:/$ ps -A | grep NetAuth
2028 ?? 0:11.22 /System/Library/CoreServices/NetAuthAgent.app/Contents/MacOS/NetAuthAgent
11282 ttys000 0:00.00 grep NetAuth
macbook:/System/Library/CoreServices$ kill -9 2028
After killing the NetAuthAgent application, everything works well again:
http://discussions.info.apple.com/thread.jspa?threadID=2131955&start=30&tstart=0