Here's a short UDF that will, at least in most cases, detect whether a window can be copied from or pasted to programmatically--for example, by Send()ing ctl-c, ctl-v. This is often disabled when programs (like your AutoIt script) run at a lower UAC integrity level than the application they are trying to operate on.
#include <WinAPI.au3>
Func _WindowIsPasteable($handle) ;accepts window handle; returns true or false whether a window will accept Ctl-C, Ctl-V
Local $bCanPaste = True
Local $hTestWindowPID = 0
Local $hTestWindowTID = _WinAPI_GetWindowThreadProcessId($handle, $hT