I have the Bionic also! It's one of my favorite devices! The 4G speeds on this phone is amazing! May I ask what app is it that you are trying to download? Have you tried to download another app & if so, do you get the same error message? If it's only happening with one app then the issue can be reported to the developers for review. Simply, provide me with the name of the app & I can look it up for additional information on how to report the error message that you are getting. If the issue is with the Market place then the best option would be a factory reset. I have posted a link on how to complete a factory reset below.
Prior to completing a factory reset, I encourage you to verify that your contacts are backed up. Backup Assistant and your Gmail account are excellent options for archiving your contacts. Once you have performed the factory reset then the device would need to be reactivated. This is a fairly simple process and the tutorial on the device will walk you through the setup process. After the device is setup then please try to download an app for the market. If you are still getting the same error message then please advise by replying to this posting for additional assistance.
Seems like I had this issue on my X, fixed it by Going to Settings>>Manage Apps>>All Apps>>Market and then tapping clear data and clear cache. Give that a go.