Two big-ticket tours have hit a couple of road snags recently, as 'N Sync and Whitney Houston have announced date changes (and even cancellations) on their respective outings.

Whitney Houston cancelled her concert in the San Francisco Bay area on Sunday, due to illness. The show, which was to be the last date on the U.S. leg of her world tour, joins a slew of previously postponed or cancelled dates in Tennessee, Missouri, New Jersey, and Washington, D.C. (see "Whitney Returns To Stage After Throat Problems Cause Cancellations").

And at the risk of breaking its young fans' hearts, 'N Sync has changed up the last week of its North American tour so that the fivesome can fit in some more time in the recording studio.