Jennifer Nettles is on vocal rest -- doctors orders. Thus, Sugarland has been forced to cancel their performances at a few shows on both the Kenny Chesney and Keith Urban summer tours, much to the dismay of the superstar duo and their ticket-holding fans.

"It's so sad when someone that I love to hear talk can't talk!" Sugarland's Kristian Bush tells The Boot. "It's a horrible thing -- it's like playing that game with my kids where I go, 'OK, no talking for ten minutes.' And the moment you tell them that, that's the one thing they want to do!"

"Your voice is like a muscle, so if you strain it, you have to heal it or else you will break it. And I don't want to break it, because I want to come back out there and see you!" Jennifer explains to fans in a video message. "I thought about trying to make up a really good story, that I was out binging on opium and absinthe in Paris. [laughs] But that's not my sense of humor."

It seems some of Sugarland's fans don't have much of a sense of humor when it comes to the performance cancellations. The message boards on various blog sites are filled with angry comments from disappointed concertgoers. Sugarland's tourmate Kenny Chesney is a little miffed by the backlash. "It was really sad to see the way some people reacted to Jennifer needing to cancel her appearance in San Francisco last weekend," he says. "We should all be concerned about her long-term vocal health more than any single show that she may not be able to do ... I know she'll be back before the summer and can't wait to have her back out there. But it's about doing the right thing, and we should all be supporting her in that."

Sugarland will release a live CD/DVD set, 'Live on the Inside,' sold exclusively at Walmart starting August 4. The Boot also spoke with Kristian about the new project and its corresponding TV special. We'll have more of that part of our exclusive interview with him next week.