Is there any difference between single and double quoted strings in ActionScript?
There is no difference.
This is from ActionScript: The definitive Guide:
String is the datatype used for textual data (letters, punctuation marks, and other characters). A string literal is any combination of characters enclosed in quotation marks:
"asdfksldfsdfeoif" // A frustrated string
"greetings" // A friendly string
"moock@moock.org" // A self-promotional string
"123" // It may look like a number, but it's a string
'singles' // Single quotes are acceptable too