At last, our long national nightmare is over.

No, it's not the war in Iraq and the continuing threat of domestic terrorism. Unfortunately, they're still here.

I'm referring instead to the return tonight of David Letterman to the CBS Late Show for the first time since Feb. 26.

The show tonight, featuring guest Billy Crystal and 18-year-old world whistling champion Michael Barimo, will be widely watched.

But will we see the same old Dave?

His previous -- and only -- lengthy absence due to illness might provide some answers.

When Dave comes back to work Monday at the Ed Sullivan Theater, he will have been gone for 34 days -- the same number of days he needed to undergo quintuple bypass surgery and then recover in winter 2000.

Three years ago, quick-thinking doctors prevented a catastrophe that, by Dave's own admission, could have ended his life at age 52.

In his first show back on Monday, Feb. 21, 2000 (the show was taped on Friday, Feb. 18, his first day back at the office), Dave came on like a new man -- energized, vigorous and ebullient, a word one doesn't usually associate with grumpy Dave.

He also brought his medical team on stage for a heartfelt thank you (it came out later that an actor was hired to stand in for Dave's vacationing heart surgeon, but I'm willing to forgive and forget all that).

But shingles aren't exactly the same as life-saving heart surgery.

Grateful as Dave might be to the doctors who helped clear up the shingles around his eyes, I'll bet we won't see a parade of physicians and nurses this time around.

The difference is that Dave's ailment was not life-threatening.

It was, however, tenacious, painful, uncomfortable, annoying and, in Dave's case, supremely inconvenient. And he might still have some lingering pain even if the shingles have cleared up visibly on his face.

And this latest medical crisis differs from the last one in another important way. I know this sounds strange, but you can ask any comedy professional and they'll tell you the same thing: a case of shingles just isn't as funny as heart surgery.

Most likely, Dave and his writers will be struggling today to figure out how to deal with shingles on tonight's show.

Do they work it into the opening monologue? Or Dave's chat segment with Paul? Or how about a Top 10 list about shingles? And what if one of Dave's guests starts talking seriously about shingles? That doesn't exactly sound like a surefire recipe for laughs, does it?

Dave's return comes just in the nick of time (less than two weeks 'til his birthday too -- he'll be 56 on April 12).

There's a war on, and no matter what he might say about shingles, we'll really be listening for what he has to say about the war in Iraq.

Welcome back, Dave.