I experienced a sudden numbness in my left arm this morning.  Just after
I completed my 4th set of deep squats.  Today was my weight training
day and I was just beginning my routine.  All of a sudden at the end of
the 4th set my arm felt like it had gone to sleep.  It was cold, turned pale,
and lost 60% of its strength.  The weight I used for squats wasn't that
heavy, I was working hard but not at 100% effort.  I waited for a few 
minutes, trying to shake the arm back to life and then continued with
chest exercises (flyes) with lighter dumbells than I normally use.  But
I dropped the left dumbell during the first set, and experienced continued
arm weakness into the second.  So I quit training and decided not to do my
usual hour on the ski machine either.  I'll take it easy for the rest of
the day.

My arm is *still* somewhat numb and significantly weaker than normal --
my hand still tingles a bit down to the thumb. Color has returned to normal
and it is no longer cold. 

Horrid thoughts of chunks of plaque blocking a major artery course through
my brain.  I'm 34, vegetarian, and pretty fit from my daily exercise
regimen.  So that can't be it.  Could a pinched nerve from the bar
cause these symptoms (I hope)?

Has this happened to anyone else?
Nothing like this has ever happened to me before.  Does it come with age?

Thanks,
Tom