Help: stripped lug bolts

[doggfarm@erols.com (John)]

I know this doesn't require much in the way of expert advice but I'm hoping
someone will see fit to respond...

I just returned from having new tires installed and the dealer handed me a
lug bolt with the bill. The threads were clean as a whistle; he claims they
didn't strip the rotor when they installed the wheel but they couldn't get
it to tighten.

What can I do short of purchasing a new rotor to remedy my situation?

I seem to recall VW listing an oversize lug bolt for the aircooled
cars...maybe someone knows if Audi does too. How long can one safely run a
factory alloy wheel w/only three lug bolts?

John