Screen Sharing - sending system keys frequently fails

Hi. I'm running Mac OSX 10.7.5 on a Mac Pro desktop and a Macbook Pro laptop.

I use the Screen Sharing application on the desktop to control the laptop.

Quite frequently, the Screen Sharing app stops sending system keys to the laptop. For instance, when I first boot up the desktop and launch Screen Sharing, I can use "Cmd-Tab" to switch applications on the laptop. Likewise, I can press F11 to hide my apps and view the Finder Desktop (as set in my Mission Control settings) on the laptop. On a regular basis, however, the Screen Sharing app will just decide to stop sending those system keys to the remote device. All of a sudden, Cmd-Tab won't switch apps on the laptop anymore when Screen Sharing is active, but instead switches them on the Mac Pro. Likewise, when this happens, F11 will no longer show the Finder Desktop on the laptop anymore, but instead shows it on the Mac Pro. And yes, I mean this behavior occurs when Screen Sharing is the application in focus and being used at the time. If I reboot the Mac Pro, then it once again sends those system keys to the remote host, but it's guaranteed that it will stop working again in fairly short order.

I have tried many things, including setting the "defaults write com.apple.ScreenSharing DoNotSendSystemKeys -bool" variable to "FALSE" (and have even tried toggling it from "TRUE" back to "FALSE"). I have also tried closing Screen Sharing altogether, then deleting all related prefs files that include "com.apple.ScreenSharing" in the filename, then relaunching. I wrote an AppleScript script to make this easier, but it only works about 20% of the time at best, and is totally unpredictable (I can often invoke it several times and it may work on the 5th or 6th or 10th try, or sometimes not at all).My guess now is that the deletion of the prefs isn't actually doing anything, and that it's simply a roll of the dice when relaunching the Screen Sharing app.

All of the pages I get when trying to Google for a solution are about disabling the sending of system keys. I want to do the opposite. I want to make sure they are always sent to the remote host when working in the Screen Sharing app. Has anyone else ever encountered this and found a solution?

Thanks,
Tyson