Am I having a "derp" moment?

So I went to use one of my two speedlights today, this one is an ancient Nikon SB-24 which has been fantastic for at least 3 years now. I plugged in the sync cord and it wouldn't fire. Fiddled with both ends of the cord, switched it around, fiddled some more, nothing. Plugged in my cheapie radio poppers and voila! It fired just fine on the first try.

What gives? I've used the sync cord with that speedlight tons of times. Why would that suddenly not work, but the radio trigger did?

have you tried that cord on the other speedlite you have? the cord maybe damage or loose.

Sync cords and PC connectors are one of the weakest links in photography reliability. Second only to discharged batteries.
Plug the cord into your flash and short the two connectors on the camera end of the cord with a metal object. Key, paper clip. If the flash fires the cord is as good as a sync cord ever gets. If it does not fire it is the cord.

Tacoman, I can't use the cord on the other speedlight as it doesn't have a pc port. It's an even more ancient Sunpak but works fine with the radio trigger via a hot shoe adapter.

dedsen, thanks. I'll give that a go and see what happens. The cord is only 3 months old, but it was cheap of course. I should probably just get another receiver.

I got both of these speedlights for free (not that they would be expensive anyway) so I probably shouldn't complain too much.