I agree with Wildman (thanks for option provided!), the issues outlined in your post are strange. Since clearing Market Cache has not resolved issue and your latter post indicates that you have a new SD Memory card, I would recommend trying two things:
1 Format SD Card Please note that this procedure will erase all data on the memory card. It is recommended to back up the data.
2 Factory Reset Keep in mind that performing a hard reset will remove ALL data including the Google account, system data, application data, application settings, and downloaded applications.