I think I've read somewhere that if you don't use a certain kind of lubricant: carbon dust or something like that. You risk attracting dirt, and similar kinds of things that lubricant can attract, that will only mess up your lock. Though I, kind of, hope not. I also experience similar difficulties opening my Kryptonite Mini: Key not turning very easily. I'm pretty sure that lube would solve that, but I'm afraid that the dirt that the lube would/may attract would in the long term, cause more harm than good.
What I put in there was some Phil's Tenacious Oil. It's been as smooth as ever since; been that way for about a year now, so, no negative side effects from it here (aside from just after lubrication when the damn lock opened WAY too easily compared to what I was used to and fell right on my toe.)
I figure if you can't use the lock due to it jamming anyway, the risk is worth it.