[Plugin: Stats] Multiple users unable to log in

I uploaded the stats plugin last night as an admin. Now my other bloggers cannot log in to the site; the site says the username and password is incorrect.

I want my users to be able to see the ststs for this particular site, but not all of my sites.

Should I create a wordpress account for this blog only? Do all of my users need to have separate wordpress.com accounts as opposed to the .org accounts they currently have?