I've had three flats on my cyclocross bike in the past couple of weeks, all of them at the valve stem. At first I thought it was the cheap rim strip that came with the "Vuelta XRP Cross for Disc or Rim DoubleWall, black anodized" wheels allowing contact between the stem hole and the tube / stem junction. I replaced it with quality tape but low and behold I flatted in the same way yesterday.

Basically it looks like they are getting cut right at the base where the stem joins the tube. I'm running about 35#'s in my 34mm tires with Kenda Q 27-32 tubes. When I put the tape on I checked for sharp edges but didn't notice anything out of the ordinary.. any suggestion?