cardstock question

[mermccau.livejournal.com]

So, I am making invites for a client of mine. To keep cost down for the client, I bought cardstock at AC Moore which was reasonably priced.

I am using a bone folder to put a fold in the cardstock and it is doing a weird thing - the paper along the crease is kind of buckling or cracking after I fold. Does that make sense? Any ever come across this? Is it indicative of the quality of the cardstock?

Thanks :)