The problem definitely existed prior to the .51 update. Seems like there are enough people between a few threads to suggest this isn't just some fluke problem. It might be helpful to get a consolidated list of maemo.org users who are experiencing the problem and see if we can get nokia to respond.
My volume just goes to the speaker off mode. I thought it was a bug because it happened every time i wanted to raise the volume.
However, I've noticed that the volume "button" is really upside down when I'm in phone mode. So, when trying to raise the volume, I pressed the upper key, which actually is the volume-down-button when in landscape mode
I just tested my volume, it's the right way up, unfortunately the phone upside down. Just kidding!
I think that was a separate bug/feature though Crotch, sounds like bug 5897, something to do with the volume button and the orientation of the phone.
When this bug occurs, the volume can be on full but the speaker outputs (almost) no sound, also, it appears to switch by itself, rather than after some sort of user input.
I had an issue with my pre-production device where the volume was regularly dropping, during a call, to practically inaudible levels. Pressing the volume up key (in the right direction) had no effect.
It got so bad that the device was unusable as a phone so, asking if this was a known software problem (and being told "no"), I got it replaced.
Exactly same symptom here. Thought it was my rubbery case covering up the hole. Been running without case for 2 days and still same problem. Problem seems localised to internal speaker as it does not exhibit the fault when connected via bluetooth to car. Cannot comment on software level etc. as got to know the device and updated 42 to 44 and then 51 long before transfering SIM and using the phone features.