I've had this for awhile and even when I did take time off it didn't seem to improve. I get a dull ache that starts at my right rear delt and goes to my forearm. It seems worse if I am sitting and have my hands on a table or desk. At first I thought it was from using the mouse so I switched the mouse to my left side. It doesn't bother me when training only when I am sitting around. Also, sometimes if I'm typing, my right forearm gets really tired.
i've had that a couple of times before, it went within 1-2 days, and was definately due to computer usage... I think it might be RSI.
Take regular breaks from the computer, and make sure your really comfortable when sitting there (such as your arm in relation to the computer desk and body).
Search google for the ideal computer setup...
OK, here comes a real W.A.G.:
Does your arm go to sleep when you have it over your head? Thoracic Outlet Syndrome isn't something I see in my office so I'm definitely not an expert on it, but it's possible you have it. The subclavian artery and vein and the brachial plexus run between your clavice and ribcage on the way to the armpit and the arm. You can get impingement of either the vessels, the nerves, or both if that space is tight. If you're leaning on your elbow or forearm that might push your humerus into a position that further impinges on these structures. If the nerves get impinged you'd expect to have pain, numbness, or tingling. If the blood vessels are impinged it might feel like your arm is going to sleep.
Other things that can hurt laterally at the deltoid/shoulder are rotator cuff problems and shoulder impingement syndrome. I would expect you would be having problems during and after workouts if that were the case.
Thanks for the replies. I haven't noticed my arm falling asleep but after reading the links it sounds as though I may have this.