[Leica] M7 shutter speed problem

[geordiepete211 at yahoo.co.uk (Peter Cheyne)]

I last used my M7 two weeks ago.  Fine.  Today I ran through the  
shutter speeds and found a big problem.

1/1000-fine; 1/500-fine;
1/250-doesn't work at all, the shutter does not even open;
1/125 & 1/60, being mechanical, are fine;
1/50-slow, more like 1/8;
1/30-slow, more like 1/4;
1/15-slow, more like 1 sec;
1/8-too fast, more like 1/15, I repeat this and about 9 in 10 clicks  
are too fast, and about 1 in 10 clicks are working as Bulb... weird;
1/4-works as Bulb; 1/2-fine;
1 sec-way too fast, more like 1/1000; 2 secs-fine;
4 secs-fast, more like 1/15;
Bulb, 9 out of 10 times it works as Bulb, 1 in 10 times it is more  
like 1/1000.

I bought this camera late May, used, from a local chain camera store.   
I'll take it back tomorrow and hope it is still in warranty.  They  
either give 6 months or one year warranties, depending on the camera  
and it's condition.

I'd like to know, before I take this back to the store, if anyone has  
had this problem, or knows what it could be.  At the back of my mind  
I'm thinking it could just be just that the batteries are low, but no  
other of my cameras behaves so erratically when the batteries are  
low.  I'm now thinking maybe the M7 is not a very reliable camera, but  
I'd love to be wrong about that.

By the way, when I say above that 1/50 is more like 1/8, I'm not just  
guestimating from nothing, I'm comparing side to side with an M6, then  
an M8.  The M6 and M8 agree (as does my ear), but the M7 is definitely  
making a cry for help.

Cheers,

Peter Cheyne