I think you should try their service - even if you think you voided the warranty doing something else. They'll probably take care of you.
If that is an absolute impossibility than I would get a larger screw and tap a new hole using the larger size, should work fine for you.
Sears hardware should have all you need for around $15 - Tap, tap wrench, new screws and drill bit.
BM's liners are hardened but not enough to stop you from tapping a hole, just take it slow and back the tap out frequently.
Good luck!