Cannot log in – "Key does not appear valid"

This morning I pull up my computer, and my log-in screen said my WordPress password was invalid. I tried different browsers, nothing worked. So, I hit the “Forgot password” button, which took me to a page to enter my email, which I did. I got an email, and followed the link to “reset” my password. This takes me back to the same forgotten password page, with a box to enter in my email address again. Only this time, it has a little red box that says “Sorry, that key does not appear to be valid”.

I don’t know what the heck a “key” is.

Let me give you background: I previously used this stats plug in, which I think is called WordPress Stats plug-in. Several months ago, it stopped working and said that I needed to get a “valid key” or something. I had used it for a year, so I have no clue what happened. I clicked the link to get this mysterious “key” and it brought me to my wordpress log-in page. I inputted my normal log-in information and it said password was wrong. After several fruitless attempts, I disabled the plug-in. I could get into my admin panel, I just couldn’t get the “key”. Yesterday, I thought I’d give it a shot again. I upgraded the plug-in and re-activated it. Again, it said I needed a key, and every time I try it says my password is wrong. Then, I noticed the plug-in was called “WordPress.COM stats”, but I use WordPress.org on my own domain. Not sure why I never noticed that, but I could swear this is the same stats program I used before on my WordPress.org blog. At this point I’m thoroughly confused and I disabled it. I was in my WordPress admin panel yesterday, writing posts, and had no issues.

Not sure if this matters, but I have several wordpress blogs on different domains.

Please help!