That would be a chainring that's bent then. You might be able to simply straighten it with some patience and a set of pliers. Looks like those are chainring bolts, so an alternative would be to replace the offending chainring, too (looks like a fairly standard 4 bolt 64/104 mm bolt circle diameter set).

Like andrewp said, concern is what you meant by pedals falling off before...was it the crank arms that kept falling off or did the pedals come loose in the crank arms themselves? If the crank arms kept coming off the chances are you've damaged the softer square tapered interface in the arm rather than the harder taper on the bottom bracket itself, and a new bottom bracket alone may not solve your problem. You seem to have the sizing down (there's two other factors, the type of threading and the degree of the taper, but with a 68mm shell it's most likely English threading (1.37 x 24) and a JIS taper (common with a crank like yours).

You might want to look at this article http://sheldonbrown.com/bbsize.html