SSH public/private keys work in Windows but not in Linux

SSH public/private keys work in Windows but not in Linux

I have a server that supports SSH Key-Auth login. I've made my key-pairs, uploaded them... etc. In short, it works--in Windows. I made the key-pair using Putty's key maker (PuttyGen IIRC) on my Windows XP box, however on my Linux box I can't "unlock" the key.