D50 (CHR) problem, I think temperature related.

I recently used my Nikon D50 abroad it was working fine for about 20
pictures then I got a (CHR) flashing indicator. Then it worked again and
then same thing happened. The manual indicated a memory card problem however
I was using this camera in temperature of -9 C which although cold I wouldnt
have thought excessive. I kind of worked out that it would work for several
pictures when coming from hotel room to outside then I would get the (CHR)
indicator, assuming once the camera had cooled down. On one ocassion when it
stopped working I took it into a warm envirement and 10 minutes later it was
working ok again. On another ocassion I used it in a warmer enviroment and
it was ok with no problems.
I am therfore assuming its a temperature problem.
Can anyone throw any light on this or has anyone else experienced this? I
was using a freshly charged battery pack.

thanks