When leaving the fort, there is a scripted sequence that plays, and the player controls are disable for the duration. Sounds like the script glitched..... on PS3, there is no fix for it. If those are the only saves you have, then you are basically screwed.
An item of note though, for future reference. This game seems to enjoy corrupting save files. The more you overwrite them, the higher the likelihood of file corruption. NEVER rely on auto/quick saves. ALWAYS make a NEW save at various points, and do NOT overwrite them.