Hi All,
I am providing this as informative, not as a criticism of any product.
I upgraded my Norton Internet Security on my Mac Pro laptop, to the latest version.
Then my problems started. System freezes, lock-ups, loss of internet connection; inability to log into Flickr, Yahoo Mail etc etc, inability to close programs, or turn computer off via the Apple icon ...
I uninstalled and reinstalled the Norton Internet Security 3 times, to no avail ... I then went hunting within my computer ... and, took a punt and uninstalled 'Glimmer Blocker'.... Result: all Norton Internet Security issues mentioned above, are now resolved ....
The above may be of assistance for others ...