Q: iCloud password incorrect but it is the right one (iMac using Yosemite)

HI,

I recently had to change my email address.  I changed the details in iTunes and iCloud.  All my iOS devices are working fine (after logging out and back in again) but today my Mac started saying it wasn't connected to iCloud.  I looked up in the support communities and discovered I need to sign out and sign back in.  When I click "sign out"  and enter the correct password I continually get an "password incorrect "error.  I have logged into iCloud online, just to check I am using the correct password, and it works fine.   There is nowhere to delete the account, which still says it is connected to the old email address.  I have been using the computer for over 24 hours since the account change and it has been okay. I also reauthorised and reauthorised the iMac incase it helped, but it didn't.

Thanks !