EPROM's usually have pretty strong legs, since it's assumed they'll be recycled a few times, but if they're mishandled during their life, the legs can get bent up a bit over time. You really have to take care removing *any* chip from a socket to avoid damaging the legs. If you use a screwdriver, lift each end up a bit at a time to avoid bending the legs too much on either end, and make VERY sure they're all lined up and straight before reinstalling. I see more damage during reinstallation than I do during removal, personally.
I keep dead EPROM's around to pull legs off of when the leg breaks off some other chip - I salvaged one Galaga board in that fashion; must have replaced 8 legs at least on the various custom chips, where the legs had just rotted off...
Alternatively, if you don't have the finesse to solder a replacement leg onto the chip - put it in a socket, and just connect the damaged leg to the respective leg of the socket, and put the newly socketed chip into the existing socket - a good idea for fragile chips even when the legs aren't broken.