Custom Plugin Causing NONCE Rejection on Custom Post Types

I created a custom plugin that uses nonces (I don’t totally understand all of the code; I used a tutorial from WordPress 3 Plugin Development Essentials), and once I activated it, the custom post-types that I created are having incorrect nonces, even the ones that aren’t associated with the plugin. I’ve used custom post-types before, and I’ve never had a problem. Some other nonces are being rejected, but the page nonce (that I’m assuming exists), is fine.

This is my main plugin code:

[40 lines of code moderated as per the Forum Rules. Please use the pastebin]

And this is the include (there’s a lot that’s not necessary, sorry):

[A further 320 lines of code moderated as per the Forum Rules. Please use the pastebin]

Any help would be MUCH appreciated. It’s becoming a drag to have to explain to the client “yes, you can hit the link and it will publish it.” No one believes me… =S

Thanks!

Jake