FAST FORWARD'S HELP FILE Rob Pegoraro

Q Google Maps' directions never send me on I-66 inside the Beltway, even when that's obviously the fastest route. Why doesn't that site like this highway?

A All navigation software can be tripped up by the quirks of real-world roads. But Interstate 66, which does not allow single-occupancy vehicles inside the Beltway at peak times, provides an extra challenge.

Google Maps is not alone in being skittish about I-66. MapQuest, Google and Yahoo all plotted a route from Arlington to Herndon that sent a driver along U.S. 50 to the Beltway, adding four to five miles to the direct route, which starts on I-66 and is provided by Microsoft's Live Search Maps.

Google Maps is a little more extreme in its aversion to I-66, as it avoids the inside-the-Beltway stretch of that highway at all times. AOL-owned MapQuest, by contrast, will send you on I-66 if an alternate route would add more than 15 minutes to the drive, AOL spokeswoman Allie Burns said.

Google spokeswoman Elaine Filadelfo said the site's developers "are currently working on determining how best to account for various restrictions so that our users can have the best overall directions." Until then, use Live Maps to double-check routes that would normally put you on 66.

The "Mighty Mouse" on my Mac has never been able to scroll down; it only scrolls up. And the cleaning procedure you suggested hasn't been able to fix that.

At the risk of sounding like Captain Obvious, take the thing back to an Apple Store and get them to replace it. Sometimes, hardware is just broken, and there's nothing you can do on your own to fix it. That's when you should not hesitate to make your problem the vendor's problem by returning the malfunctioning product.

Rob Pegoraro attempts to untangle computing conundrums and errant electronics each week. Send questions to The Washington Post, 1150 15th St. NW, Washington, D.C. 20071 orrobp@washpost.com. Turn to Thursday's Business section or visit washingtonpost.com anytime for his Fast Forward column.