Sound Dropout while taking movies on G2

[Antares68]

While taking a few movies out and about yesterday I noticed that on playback that on two different 30 second shoots there was a place (lasting for about 1-2 seconds on each) where the sound seemed to drop off completely, and then it came right back again. The shoot was done in a very noisy environment (in a packed London bus!), but this dropout in sound was certainly not caused by me inadvertantly putting my finger over the microphone slot. By the way, I when I do cover the microphone, there is no appreciable loss in sound anyway, so I am at a loss how to explain these two incidents. Other than that, I have taken many 30 second shoots and nothing like this to report. I am using the 1GB microdrive for storage.

Thanks for any suggestions...

Mike