Norton application blocker slows down shutdown

When the application blocker function of Norton firewall is turned on, the shutdown time is around 1 minute. When it is turned off (only the application blocker not the entire firewall) then the shutdown time is normal (few secs, ssd drive).

Installed Version: Norton Internet Security 5.2 (59), german version.

Installed OS: Mac OS X 10.7.3 on iMac

There seem to be difficulties to shut down properly this process (checked in verbose mode).

I tried already a complete remove and reinstall of Norton but it did not change anything. This happens now since some weeks.

How can this be fixed?

Thanks for any support.