That's because it is officially all of a sudden and not all of the sudden. Mr. Rewrite spotted this today while cruising Paul Brians' (cue angelic chorus) Common Errors in English Usage site for ideas. Garner's Modern American Usage backs this up.
All of a sudden is an idiom used when something happens abruptly and without warning, like regular unleaded topping $4 a gallon.
Mr. Rewrite did a thorough 15-second search and couldn't find the origin of all of a sudden. Here's all he can offer: Top usage guides say to do it that way, and you risk a tongue-lashing by those smarter than Mr. Rewrite if you say or write it incorrectly.
All of a sudden Mr. Rewrite wants to see how those paid to know better deal with this idiom. The answer: Not very well. Google News indexes hundreds of articles containing all of THE sudden.
Here's a grammar error amusing to everyone but taxpayers in Missouri. The first copies of that state's redesigned license plates say "Show Me State" rather than the correct, hyphenated "Show-Me State." It took an English professor to point out the problem.
Meanwhile, Mr. Rewrite was amused to see two significant errors in an Associated Press story about this mistake:
- It refers to the plates as "newly-designed." You don't hyphenate compound modifiers that begin with adverbs ending in -ly. How does Mr. Rewrite know this? IT'S IN THE AP STYLEBOOK!!!!
- The second paragraph begins: "Motorists on Monday were issued ..." This is astonishingly passive. It's easy to flip and make active: "Motorists on Monday received the ..."