My car whines - my kids are grown, I don't need any more whining!

I seriously love my car - it’s a 2000 Honda Accord coupe, a real midlife-crisis-mobile (red, leather interior, spoiler, moon roof) with about 112,000 miles on it. Last spring I had the rear oil seal replaced to the tune of about $1300, and since then my car has made a whining noise, sort of a cross between a dentist’s drill and the “Flight of the Bumblebee.” It generally makes the noise when I’m accelerating and stops when I reach cruising speed, though sometimes it makes it when I’m idling, and sometimes it makes it when I’m at cruising speed too. Sometimes, there’s no whine at all. The guys in the shop (a shop highly recommended on this website, by the way) looked at the car and said they can find nothing wrong.
My question: should I be worried about this? Should I have another shop look at the car? Should I be afraid to drive? And, how much will this cost me?
Thanks, guys!

You need a second opinion. If you could better describe the location of the noise when idling that would be helpful. The first guess would be a serpentine belt or tensioner.