Another vote for Velox rim cloth tape. Also, use a cotton ball or used drier sheet to go around the rim--they will snag on anything and if there's something in the rim, you'll find it! I've found that some "glue" just doesn't work as well. Rema vulcanizing fluid is what I've found holds best. You say the hole is always near the valve--are you using the nut on a presta stem, and tightening it down on the rim--if you are, don't do that. If you want to leave the nut on, move it up on the stem, can always put it down toward the rim when inflating.