Deflated tube: Is it me, or it is the rim tape?
Rim strips, proper ones from a bike shop, last a long time and are immune to the wear shown on your picture. It looks like the strip left the hole exposed enough that the base of the stem was allowed to make contact with the rim. 

My advice is to take off the rim tape. Clean the interior of the rim with acetone. Take some fine grit sandpaper (1600-2000 grit) and gently rub it into the hole from inside of the the rim. That will help smooth out any possible burs. Then install the rim strip (not tape) and for one last good measure use a tube that is one size smaller than you usually do. It is curious how the tape shifted. Perhaps the stem wasn't perpendicular. At any rate, the smaller tube would decrease the chance of this happening with no ill effects.

Good luck!