A few years ago Coldfusion made a security upgrade that caused CFWebstore to reject valid logins. When you enter in your username and password you just bounce back to the same page with no error message. If you close out your browser and then reopen, you should be able to login.
Here's the quick fix. Login to Coldfusion Admin > Server Settings > Memory Variables. Check 'Use J2EE session variable', click 'Submit Changes', and then restart the Coldfusion Server for the changes to take effect.
This problem still happens on new servers because J2EE is not turned on by default.