I've found that when using the crop tool if I unlock it for an image it tends to stay that way, but usually if I unlock it this is done for the exception, not the rule.
For some silly reason once I've unlocked it, even if I subsequently lock the thing down it remains unlocked for every new photo I move to. Even if it was locked before.
Why is this happening?
Try selecting any image and then go to Develop choose the crop tool. Set dropdown to original and click the padlock to lock. Click on the word reset, then click on the word close. Hopefully it should stick.
There's a lot of people out there with this same question and just as many wrong answers. 99jon, yours is the one that actually works!
It works the other way too. If you can't free crop, this will toggle it back.