Screen Capture Can't Be Saved

After upgrading my iMac to OS X Lion (10.7) everything works (or at least seems to work), until I tried to do a screen capture with the built-in tools.

Things that worked:

• Capturing the entire desktop to file
• Capturing a selection (using the cross-hair) to file
• Capturing the entire desktop to the clipboard
• Capturing a selection (using the cross-hair) to the clipboard

Things that didn't work:

• Capturing entire windows to file or the clipboard (SHIFT-COMMAND-4 + SPACE / SHIFT-COMMAND-3 + SPACE)

All I got was a weird notification box with the message:

Screen capture can't be saved

The console application also showed an error message:

12/16/11 1:40:08.762  com.apple.SystemUIServer.agent: screencapture could not capture window 3c

Lurking around the Interwebs, I found this seem to occur after an upgrade of the OS, but real solutions are hard to come by.

This is what I did to solve my problem:

• Remove the screencapture PLIST (preferences) file (~/Library/Preferences/com.apple.screencapture.plist)
• Copy a com.apple.screencapture.plist file from a working OS X Lion environment and place it in the correct location on the troubled OS X installation.

That seemed to result in two com.apple.screencapture.plist files (one with an additional extension of .locked). I removed the .locked file, rebooted the iMac, and screen capture worked again.

I must mention that I didn't see the .locked file initially. Could be that it existed before. In which case I probably did more than was required to get things fixed....

Update on Thursday, February 2, 2012 at 20:29 by Willem

Turned out that the .plist problem wasn't the cause of my problems, since I ran into the problem again today.

For some reason the capturing of Windows (SHIFT-COMMAND-4 -> SPACE) borked again. So I tried the steps I descibed above, but to no luck. looking into the Console app of OS X I found the following error messages;

2/2/12 4:20:57.153  com.apple.SystemUIServer.agent: No images found for wid 53
2/2/12 4:20:57.153  com.apple.SystemUIServer.agent: screencapture could not capture window 35
2/2/12 4:21:25.511  com.apple.SystemUIServer.agent: No images found for wid 32
2/2/12 4:21:25.511  com.apple.SystemUIServer.agent: screencapture could not capture window 20
2/2/12 4:21:45.773  com.apple.SystemUIServer.agent: No images found for wid 282
2/2/12 4:21:45.773  com.apple.SystemUIServer.agent: screencapture could not capture window 11a

Through sheer luck, I bumped into the solution; while I was trying to solve this mystery, I needed more desktop real-estate. So I switched on my second monitor (connected through DisplayPort). After a couple of minutes I tried the capture again, and it worked. Up till that point, I only have been playing with the plist files from my laptop or server and copying them to my iMac..... **FLASH**

Looks like that when the screen settings are set to Mirroring, and the external monitor is switched off, you run into this weird behavior. Rebooting with no monitor attached (switching it off doesn't seem to do the trick) also solves the problem, but introduces the one where you're missing screen real-estate....