This is just a quick note for my own sanity, and hopefully the sanity of others.
From time to time my Gmail password stops working on my iPhone. Seemingly for no reason, the mail application complains that my password is incorrect, even though the I haven’t changed my password, or the settings on the phone.
What’s actually happened, is that Google has locked remote access to the account for some reason. This happens to me about once every three months. A quick search on the internet shows me that a lot of other people have run into this problem too, but very few of them have found the resolution.
If this ever happens to you, all you have to do is go here, and complete the unlock form.
 You may also have to re-enter you password one time.