"Problem with iCloud" message keeps coming up
I have a MacBook Pro and use Safari and ever since I upgraded to Yosemite (and maybe that's just a coincidence--I have no idea), I keep getting a message that pops up saying that iCloud cannot connect to *********@gmail.com. It gives me a link to System Preferences and suggests that I click there to fix the issue. The problem is that when I click there, it asks me for the Apple ID password for ********@cstone.net (which is an account that I have, but NOT one that should be associated with my iCloud account). I enter every password I can think of and then it tells me if I forgot my password to click here. So I do and I enter that email address to have it send me a link to reset my password and it says it sent but nothing ever arrives. Elsewhere I am able to log in with my gmail account and the password that I know and cstone.net is not listed among my email addresses on my account. So where is this coming from and how can I get this annoying message to stop popping up on my screen? Thanks!
MacBook Pro, OS X Mavericks (10.9.4)