We are looking into this issue and hope to find a solution quickly.
However, can you please try something for me? If you select the save you wish to play, then select the last Episode you played (would be Episode 4) on that save and hit Play, the game should start you at the beginning of Episode 4. Once there, exit to the Main Menu, and tab back over to Episode 4 and the Continue button should be available. Also, if you select Rewind, you should see all the available checkpoints, up to where you last left off. Try to load Episode 4 and you should start where you last left off.