A "temp" solution is to insert a small piece of thin wire into the "female" end and carefully start the "male" and snug up.
  This won't work if your constantly loosing and tightening it, but will extend the useful life until you find a better solution.
  A little Lok-Tite applied to bolt threads will help keep the bolt from backing out. Use the kind that doesn't set up like ceramic.

"The threads are not stripped......rather, the Allen nut head is rounded off...... "

  Are you saying that the Allen nut head won't except an Allen wrench, to tighten or remove it? IF so, you can by special extractor bits "easy outs", that allow you to remove bolts/screws with damaged heads.
  SEARS sells a nice set, fits in electric drill. Some require you drill the head out a little, the better onces are machined to dig in when you reverse the drill, extracting the bolt.

22 bucks for the internals..................I got it tonight........

Should have it in 2 days..........

Thanks all.

Later,

Geo

I had the exact same problem last year.  2 out of the first 3 towers I was moving to a new set of bars stripped.  I didn't even bother to try the fourth.  Very discouraging!

I called Yakima to see if they would honor their "satisfied for life" guarantee.  No dice.  They said the warrantee had run out the previous year (I guess I lived too long!).  Anyhow, after some more complaining, I found out that they had completely redesigned the Q-towers, most likely because of this very problem.  The bolt heads on the original design were made from steel that was just way too soft.

Rather than turning a cam like the old design, the bolts in the new towers tighten up a clamp.  It puts much less stress on the bolts, and it looks like the new bolts are standard (i.e. harder) bolts.

Yakima graciously sold me two sets of the new towers for the price of repair parts for the old towers.  This was after I pointed out that I really didn't want to buy replacements that were also a defective design.