This happened to me also with several apps. There are two solutions i found to work.
1) This is a fix, which may or may not have added bennifit to you....I downloaded an app called Market Enabler..it fakes your phone into thinking its on a different service provider. I chose sprint, and all my apps were accessable to me again.
2)this seemed to be a better fix, and ultimately allowed me to delete market enabler. I just went into manage applications in the settings menu, then chose market, and clear data...VOILA. Problem solved. Sometimes i have to do this when i connect my phone to computer, but then after i clear the data, all better. HOPE THIS WORKS FOR YOU TOO.
