I got the same issue. Login to Adobe Community works fine, but Kuler doesn't accept the ID/password.
any help would be welcome.
Thanks a lot and best regards,
On the Kuler home page https://kuler.adobe.com right under News & Features is an entry for Login Issues? saying "We are working to restore login issues with Kuler. Please have patience."
I agree that the notice could be more visible. I have been in communicatioin with the Kuler team and they are working to resolve this issue as quickly as possible.
The issue has been fixed.