Sorry to hear about that.
I had a very similar experience after dropping my 580 EX II. I sent it in to Canon for repair for around $150.00 (don't remember exact amount). Basically, they replaced the insides and it works fine.
I was out earlier taking some pics and my 430 EX flash just stopped working! I was using it in manual mode at 1/4 power to help freeze the movement on some Dragonflies I was photographing. However after about 6 or 7 exposures it just would not flash. I have tried 3 sets of batteries with no joy. It seems to power up OK and the red "Pilot" light quickly shows it is ready but then it will not fire on or off the camera, even pressing the "Pilot" button will not trigger it in Manual or ETTL mode. If I put my ear next to the flash gun I can hear a VERY faint beeping at a rate of about 1 beep per second.
Has anybody out there any idea of what might be wrong? Although not a new flash it has been very rarely used so I wouldn't have thought it would be the tube - but I have virtually no idea on flash guns so any advice would be appreciated.
Cameras: 1DXII,5D III, 5D II, EOS M Lenses: 24-70 2.8 II IS, 24-105 f4L, 70-200 f4L IS, 70-200 f2.8L IS II, EF 400 5.6L, 300 2.8 IS II, Samyang 14 mm 2.8 Flashes: 600EX-RT X 2, ST-E3-RT
Plus lots of stuff that just didn't work for me