Screen fades out randomly

[snownutt]

Hi everyone ...newbie here .

I recently recived a Garmin venture hc for christmas this yr . New to the GPS world and Im now having a issue.
I went to use the unit for the 2nd adventure in the snow this past wknd  and the screen fades out at random, sometimes with in a few min after start up and sometimes after time has past ....1/2 hr...1 hr later .
Is this a unit defect or did I bugger something up ?
The only thing I have done since the 1st time I used it (and it work fine ) is I downloaded from the unit to the pc. It asked me if I wanted to shut the unit off after transfer , I did and then put it up.

Should I re-load my maps ?... is it glitch in the software ? 

Any insight

Thanks..
snownutt

[maps4gps]

I would give Garmin tec support a call on this.  It might be a drop in power due to cold batteries, but Garmin should advise you on this.  Any similiar performance indoors?