Oh my aching back

So I busted myself today.  I was at the gym this morning and on the agenda (no, not checking your putenda) was legs, shoulders, then abs.  Legs went smoothly, and shoulders started out ok.  I warmed them up with the wussy set, then moved on to the normal weights (which are not very heavy).  I was standing on an inverted bosu so that the ball side was on the floor, causing me to balance and work my core.  I had an 8 pound dumbbell in each hand and was executing the side lat raise when I heard an unnatural crunch.  It came from my back, just beyond the shoulder blade, but before my spine.  And I am so smart that I finished my set and proceeded to complete my shoulder routine and them move to abs before going home for a shower.
I went in to the office like normal and I had issues.  First of all I was quickly losing range of motion in my neck making it painful to properly switch lanes on the highway with the necessary turn and look beyond the mirrors.  It was also gradually getting more and more uncomfortable to sit up straight in my chair at my desk.  Crossing my legs even began to pull on this spot.  By 9:30 I was calling the doctor’s office.  They said they’d take me at 10:45 so I took it.
It only took the doc about 20 seconds of feeling my back to determine that I have a muscle in spasm.  There’s huge knot exactly where I felt that crunch.   Her instructions were to go home, take 600mg of ibuprofen (three times a day) to ease the inflammation, apply moist heat, and don’t exercise my back or shoulders for a few days.  Ick.
Messed up thing is that I don’t even understand why it happened.  I was executing the raise properly.  I was moving slowly and being very careful about what I was doing.  Guess I can’t win ’em all.
J