If you use multiple identities, the GMail configuration must be done while as the identity associated with the GMail account. If this is not your situation, see below, otherwise you should remove the GMail configuration while as the identity that created it (use the 'Delete Profile' button) then switch to the GMail identity and create it.
Note: In the case of the above situation, the POP3 and SMTP hosts associated with first creating identity may have been replaced with the ones for GMail.
If identities is not your issue, is this a new GMail configuration or had you been using it and are now checking out the v4.81 beta?
If you use multiple identities, the GMail configuration must be done while as the identity associated with the GMail account. If this is not your situation, see below, otherwise you should remove the GMail configuration while as the identity that created it (use the 'Delete Profile' button) then switch to the GMail identity and create it.
Note: In the case of the above situation, the POP3 and SMTP hosts associated with first creating identity may have been replaced with the ones for GMail.
If identities is not your issue, is this a new GMail configuration or had you been using it and are now checking out the v4.81 beta?