What causes "cam walk"?

I hear ya' man. Like 33IMP said, may be worth a try. I feel for the guy this happened to. My engine is now in the shop for a rebuild. I'm using a solid roller cam & want the setup to live without spending a whole lot more than I've already done.
I can completely relate. Sometimes it seems like the spendin never ends. If anybody can sympathize with that, it's me.