My vote is bad site. Bad sites can be caused by a lot of things-scar tissue, the angle of insertion, the absorbsion ability in that area, etc. My very first line of defense for "unexplained" high glucose is changing my pump set without fail.
Someone asked this before and I did not see an answer--did you check for air bubbles? No matter what anyone says about the "O" rings in the insulin cartridge, I ocassionally get bubles large enough to effect my glucose readings, especially since I take really small amount of insulin.
Also, the correction with a syringe is a great thing to do. Let the pump calculate,fill the syringe and inject, clearing the calculation on the pump.
Additionally, if I am over 200, I always bolus more than an normal correction. It just seems to work better for me.
Let us know how it all turns out!