Short answer: don't take chances, see a sports medicine doctor/physical therapist for help specific to your condition.
Long answer: I shoot year around, and have been working out in the gym regularly for 30+ yrs - still in Aug 2010, I suffered a left shoulder impingement from -? (probably old age, lol). It didn't affect my archery at first, so I kept on shooting. In Nov 2010 - a slight discomfort grew into pain so bad that I was looking at the end of my vertical bow career, and hello crossbow. I cut archery practice to 1 arrow a week, and restricted shots at deer to 15 yds. When I wasn't getting better, I went to a sports medicine orthopedist in January, declined his initial offer of a cortisone shot, and started physical therapy. I followed the exercise regime the PT recommended, along with the warm ups/stretching. She pointed out that I needed to improve my posture (no slouching) and develop all the muscles that support the rotator cuff. Today, I can shoot my bow without any discomfort and I've recovered 90% of my mobility. I throw rose petals in the path of my PT, she knew her stuff...
-fsh