Occasional a620 flash shots are completely blown out when prev/next shot is not?

This has happened occasionally and I'm curious why. I'm afraid I don't recall any details regarding settings, but I think (not sure) it has only happened on close-up shots, though not necessarily macro:

one shot will be normal, while the next, with identical settings, will be extremely over exposed. The flash also makes a much louder "pop" noise. The very next shot will return to normal, though I've had it alternate back and forth a couple of times when it last happened - intended to note the settings and save examples but got distracted and forgot.

It may be that the flash is on auto. I'm not clear on the flash control, since M mode has just three possible settings while other modes have a greater number of steps the flash can be set. I'd also like an explanation of that if someone has one.

Even more than wanting to know how to avoid this I want to make sure it isn't an indication that there is a problem with the camera.

Thanks

Can you post an example so we can see? A picture is worth a thousand words.

Sure - though it might be a bit before it happens again.

Thanks

You don't have any from what you've already shot to show us?

http://public.fotki.co​m/FitzhughL/flora/refe​rence/
Note that the images are not displayed in the album in the order taken - the file names do indicate the order, though.

I managed to reproduce it, this time remembering to upload the pictures. As with the most recent previous time the pictures in question are night shots of roses. I was unable to reproduce it taking pictures of various other objects and so I just tried this again, and it happened as before. I noticed that it seems to alternate between proper and over-exposed, and think this was what happened before.

The only difference between the pictures in the settings part of the detail version of the picture review display on the camera is the histogram, as to be expected, and the file size, which makes sense as well. However, all the rest are the same for each:

Av
1/60
F8.0
EC=0
Evaluative
AWB
FC=0
MF

Note that although the flash made a louder "pop" sound and it certainly looks like the flash might have fired brighter, the flash setting is the same, and the composition is arbitrarily close to identical. Seems to happen on the second shot taken in quick succession, and again on the fourth, or perhaps there was enough pause between my taking the pictures that it is essentially the second again. Picture 029 in the album was fine (as far as this is concerned - didn't even worry about careful focusing), while 030 shows the problem, and again. The problems all happened in closely following second shots.

Any ideas? Just seem a bit odd.

Have you tried taking other flash shots of other subjects in quick succession? What if you wait 10-20 sec. between shots? What I'm wondering about is the possibility that your flash hasn't fully recharged after the first shot and is completely dumping the capacitor for the second.