A number of Mac users have noticed that the 10.5.5 update to Mac OS X disabled functionality in the Screen Sharing application, and caused other problems as well.

The recent update to Leopard, Mac OS X 10.5.5, provided a number of enhancements related to system reliability and security. One change was not welcomed by many Mac power users—the downgrading of the Screen Sharing application, which comes bundled with Leopard, removing some of its advanced features.

Many users had made use of a hack that revealed hidden toolbar buttons and sliders available only in the advanced Apple Remote Desktop client (which costs $299). The hack enabled useful functions like cross-system clipboard capabilities, remote screen capture, and granular control over display quality. But the upgrade disabled these advanced functions in the new (downgraded) Screen Sharing application.

Strictly speaking, it was not the 10.5.5 upgrade that caused the Screen Sharing downgrade. If you haven't installed this yet, notice that when Software Update checks for new software from Apple, it will display not only the "Mac OS X Update" (10.5.5) but also a "Remote Desktop Client Update". (See the image below.) The Screen Sharing application is, of course, an Apple Remote Desktop client, which is affected by this other update.


Several bloggers have noted that Apple wasn't really crippling the Screen Sharing app, they were simply plugging the holes that enabled this hack to work. Whatever the case, the situation upset enough people that workarounds were devised and posted. The most common solution (and the simplest) is to restore the old version of the Screen Sharing app. If you have backups performed by Time Machine, or a second Mac that you haven't upgraded yet, this is relatively easy. It's recommended that you store this backlevel version of the app not in its original spot (/System/Library/CoreServices/) but in another folder (e.g., the /Applications/Utilities/ folder) where you should rename it as something like "Old Screen Sharing.app". You can then invoke this app to make use of the advanced functions. (What you're losing in doing this is whatever security and reliability enhancements were added to the new version of the app.)

The other approach is a bit more sophisticated and requires that you have Xcode installed. This method is described in Rob Griffiths' article in MacWorld, where he also includes a video that explains the process in detail.

Some people (myself included) experienced problems more severe than just the disappearance of hacked-up functions. For a while after the upgrade, I found I could not use the Screen Sharing app to connect to other Macs in my network at all. There is a discussion thread on Apple's web site in which users have described the problem. Apparently, it should be fixed by clearing out Kerberos tickets, either by deleting the associated .plist files or by opening the Keychain Access app and deleting any existing passwords associated with the remote machine. Since rebooting the client machine is supposed to clear out Kerberos tickets automatically, just doing a restart might do the trick. (It did for me.) If you see this problem and rebooting does not fix your problem, you may want to monitor this thread. Note that using the numeric IP address worked for some people, but my guess is that this is because they hadn't attempted a connection to the remote machine previously using the numeric IP address, and thus there were no cached passwords or tickets that needed to be cleared.