Existing users, 
Safari 4.0 is out of beta, and the final release breaks compatibility with PithHelmet again.
Restore PithHelmet functionality by following this procedure:
Navigate to Library/Application Support/SIMBL/Plugins/PithHelmet.bundle/Contents and edit the info.plist file with TextEdit - below where it says <key>MaxBundleVersion</key> there's a number you should change to 5530.17 from whatever it was before.
After doing that, PithHelmet and Safari 4.0 will play nice.
PithHelmet
Safari plugin adds content filtering & site preferences.
Version: 3.0b2
Enable PithHelmet on Safari 4.0 final release
Feedback Type: Usage Tip
Contributed by: risenphoenixkai Monday, June 08 2009 @ 01:24 PM PDT
Product Platform: MacOSX
Used Product For: Over One Year
Recommend Product: YES
Comments
Enable PithHelmet on Safari 4.0 final release - Soane
Many thanks risenphoenixkai, your fix works and is greatly appreciated!Tuesday, June 09 2009 @ 10:29 AM PDT
Enable PithHelmet on Safari 4.0 final release - nhav8or
Following your steps, I get to pithhelmet.bundle but don't seem to have "contents" and am unable to get TextEdit to open any of it. What am I doing wrong?Tuesday, June 09 2009 @ 03:14 PM PDT
Enable PithHelmet on Safari 4.0 final release - :: MILE ::
If it's really that easy (and it may not be for the many people not as tech-savvy as many of you) it's actually a bit sad that the developer doesn't seem to bother providing a fixed version…!? :(Wednesday, June 10 2009 @ 07:43 PM PDT
Enable PithHelmet on Safari 4.0 final release - :: MILE ::
Oh, and also the fix only works if you already had PithHelmet installed before updating to Safari 4…! If you download it now and try to install it won‘t let you… :(((Wednesday, June 10 2009 @ 07:45 PM PDT
Enable PithHelmet on Safari 4.0 final release - brian163
Thanks risenphoenixkai. You beat me to the post. ;-)Reply to This
Monday, June 08 2009 @ 01:40 PM PDT