AidanS: You don't two factor authentication enabled on that Gmail account by any chance do you?

Dairyxox: You don't use a VPN or DNS service (think Global Mode) do you?
Google might be thinking you're overseas and blocking access?

PoHq: You need an app specific password by the sounds of it. See screenshot below.

Geektastic:

No, I don't think so.

richms:

Geektastic:

No, I don't think so.

Well you should.

Just make sure you record your app passwords somewhere as I have not found a way to get google to redisplay them if you need to reenter them.

Geektastic:

Isn't recording passwords sort of against the whole point? ;-)