I guess it all depends on whether "sudden" is definate or indefinate.
I saw something along this line in a short, short blurb somewhere. I tend to agree with it.
Common usage is "All of A sudden," but many people use the other phrase.
I'd never actually heard the other phrase until today, and did a search on the web. The funny thing was the people use both versions in the same piece of writing! The "all of a sudden" idiom dates back to the late 1800's, if not earlier. I couldn't find anything to date when the other phrase started showing up.
Cheers,
(Why the heck am I up at 1AM posting messages about idioms gone awry?)