I have a problem with AppleScript and System Events.
I have check \"Enable access for assistive devices\" in the “Universal Access” preference pane in System Preferences
Similar to the post on this page about Mac OS X 10.9 (Mavericks), to resolve this issue on Mac OS X 10.8 (and likely on earlier versions of OS X also), you need to ensure that the "Enable access for assistive devices" option has been enabled in the Accessibility pane of System Preferences.
The problem is not the assistive devices. AppleScript seems to incorrectly return that error code when it tries to access windows of a process that can never have any windows (in my case it was "Google Chrome Helper").
You need to catch the errors. This works for me:
tell application "System Events"
set procs to processes
set windowPositions to {}
repeat with proc in procs
try
if exists (window 1 of proc) then
repeat with w in windows of proc
copy w's position to the end of windowPositions
end repeat
end if
end try -- ignore errors
end repeat
end tell
return windowPositions
returning a list of coordinate pairs, such as {{1067, 22}, {31, 466}, {27, 56}, {63, 22}, {987, 22}} – is that what you were trying to get?
On Mac OS X 10.9 you actually get the same error when the AppleScript Editor is not allowed to use Accessibility.
Here's how you enable it:
Go to System Preferences > Security & Privacy > Privacy > Accessibility.
Then, just check the checkbox left to the AppleScript Editor and the error should be gone.