HELP! Messages will no longer longer on Mac

Hi folks,

For some reason, I cannot seem to be able to use Messages on my Mac anymore, accept for Bonjour.

When I go onto the 'accounts' section in its prefs, it says iMessage is inactive, but I'm not able to active it when I click on it. Also, I cannot delete the iMessage account; the minus sign won't allow me to click and highlight it.
When I try to add an account by using the plus sign, I can choose Google, Yahoo, AOL, and other; iCloud/Messages isn't listed.

Any idea where I can find the pref to trash it? Will that work like it did back in the iChat days?

Also, very interesting...

When I boot from my other internal drive, Messages works perfectly! Unfortunately, I don't like to use that drive as my boot drive. If I try to drag one version of Messages to the other hard drive, it won't overwrite it.