Originally Posted by santiago

I had something similar happen to me. I have an entry level Kona hardtail that comes with the Truvativ 5D cranks. The crank arms are made of a really soft alloy and I got the first thread or two mangled while trying to put my pedal in not too long ago. However, once I noticed it was a problem I stopped trying to force it in.

I brought the bike to my LBS and they chased the threads with a tap and it was perfect. The mechanic at the shop told me that they have installed helicoils with success in cranks that were even used for downhill. I suspect the helicoils would work well on a nice allo that is found on higher end stuff. My Shimano XTR and my Shimano road cranks are really nice and you don't see the metal flaking away like on my Truvativs.

Try your LBS to see if you can have the bad thread tapped to see if that helps.