Ran across an interesting (new?) issue with gmail this morning when I tried to add my daughter's gmail account to a webOS device. It kept rejecting the password with the 'invalid credentials' message, and I knew I had typed it in right - even pasted it in from Keyring the second time. I checked a while ago via the web and found a couple of email saying the login attempts were blocked this morning. That led me to this page, that says they are blocking access by 'less secure devices or apps': https://www.google.com/settings/security/lesssecureapps
If you already access your gmail account on your webOS device, you're probably fine, but if you try to add one and repeatedly get an invalid credentials message, check that page, where you can turn off this restriction.