Flash not firing

I've been having the problem of my SB600 not firing. The last 2 weddings I've done, I've had the same problem and it seems to happen right when the bridal party starts walking down the isle. I've taken it to the camera shop where I bought it and of course it worked every time. But it's happening more and more and I have no idea what's wrong. Is it how I have my camera settings? I don't think I've changed anything. I've read my manuals, I put in new batteries, I've cleaned the contacts, and make sure that I haven't used it in a while so that its not overheated. The thing is, I always rent a back up flash (SB800) and have the same problems with it, so maybe its my settings or my camera. Any suggestions? I'd appreciate any info or advice!! (I have a Nikon D90)
Thanks!!

If you are slaving it, may have radio interference, or light interference, depending on your connection type.

But if its doing that connected to hotshoe, then I'd say its an issue with the shoe. Try firing it in manual mode only and see if those problems arise again, or somehow the mount might not be tight enough and contacts lose connection. I have a light with a slightly clipped part on the mount, if its not sitting on the shoe right, it wont fire.

Are you using the Nikon CLS system? And are you using the pop up flash on the D90 as the trigger/ commander? If you are, what is the distance? And are you making sure the eye of the SB600 is facing the commander?

I'm using the flash on camera and I always shoot in manual mode. It very well may be a bad connection, I'm just confused on why it works ok at first and then when I need it the most, it fails me (or vice versa :rolleyes: ) I just can't help but think it must be something I've changed in my camera since it does it with the SB800 I rent as a back up too. It just remains a mystery to me. If it didn't do it with the other flash I would say it has to do with my flash and I would consider sending it in or buying a new one. It's just a mystery to me and I'm so frustrated especially with wedding season right around the corner....

[QUOTE=Anbesol]If you are slaving it, may have radio interference, or light interference, depending on your connection type.

But if its doing that connected to hotshoe, then I'd say its an issue with the shoe. Try firing it in manual mode only and see if those problems arise again, or somehow the mount might not be tight enough and contacts lose connection. I have a light with a slightly clipped part on the mount, if its not sitting on the shoe right, it wont fire.[/QUOTe

Were you referring to Manual mode on the flash? I'm sorry, I thought you meant my camera settings.

Have you tried doing the 2 button reset on your camera? It could be some setting you have wrong. That might fix it. Could be a metering problem?

Yes I was referring to manual mode on the flash, my thinking is that if you don't use the TTL metering then all it needs is that main contact, the one center contact to fire.

When a problem is hard to duplicate, that makes it hard to diagnose as well.

If I remember right, Grandpaw (user of this forum ) had a similar problem, it was some setting on his D90, hopefully he'll stop by and tell what he did to fix it.

Yes reset your camera and flash settings. Take a damp cloth and clean both the hot shoe and the contacts on the flash.

The problem I had was corroded battery contacts, Jeff

I've tried all of the above and it seems to fire everytime. I guess the big test will be when I have an actual event. Thank you everybody!