Someone logging into your server with the given key, and has replaced sshd with a malicious but poorly written version?

Posting your private key, if this isn't a joke post, is a bad idea. I recommend you remove it from this site and any others you may have posted the same question to. You should generate a new key pair. You might want to consider wiping and reinstalling your server - depending on whether you were configured to accept keys instead of or in addition to passwords.

I hope your username isn't trivially derived from your forum name or email address, or anything else in your profile here, and that your password is strong.

wow, do i feel stupid. so the private key is basically what i use to log in. what's the public key then? i thought i was good with computers but with this unix stuff i feel more and more like an idiot. can someone please explain how to use ssh properly?

Basically when you have a private/public keypair the private key is held by the owner of the keypair and the public key is given out to those needing it.

Thus when you use a private/public keypair to replace a password you give the public key to the server . (with ssh the public key is stored in a file in the /home/username/.ssh folder on the server), you can give the same public key to multiple servers without any risk (Something you cannot do with normal passwords).

When the server uses a public/private keypair for encyption the server keeps the private key to itself and gives the public key to anyone connecting to it.