Hmm, at this point, my next step would be to open up a terminal and run "df" to see how much space is allocated to the various partitions. Also, "mount" to show how the partitions have been mounted. I don't know how handy you are with a unix shell, but you could post the results here and we'll take a look...

(Also, I should ask, have you installed any software on the phone that might impact the photo app?)

Edit: Michaaa62 beat me to the punch.