Could cheap flash cable upset my G7?

I just bought a new, dirt-cheap cable off Ebay as my previous one (also cheap and nasty) had a broken wire and no longer worked.

Last night at club used it for the first time and  worked fine for a half a dozen shots, then began to give the the "No valid file to play" message in playback.  Stopped/started the camera a few times and it played back again.  Then I found that several of the latest shots were missing altogether from the card.  Time to turn off the G7 and FL500.

At home I put the FL500 straight into the hot-shoe and had a play.  Same problem, with or without the flash, no valid file to play message and nothing playing back at all on the camera.

Put card into computer to download what was there, and everything was there including what the camera couldn't see!  Formatted the card, put it back in camera and all appears to be working normally again with the flash and playback.  (Though haven't tried cable again.)

So I am left wondering if the flash cable has corrupted something in the camera, do I have a faulty card, or even a third possibility - could the flash be developing a problem?  As an aside, the last time I used it (on camera) it refused to turn off and I had to take the batteries out.  That hasn't happened again.

My first thought is to ditch the flash cable.  Anyone else had any issues with those cheap, curly cords?  (Only labelling on it is "TTL-O off-camera shoe cord DSLR Kit")