Can t Access Gmail iPhone 3G

When you created the account, did you use the Gmail account preset or did you select Other followed by manually entering the incoming and outgoing server info?

Regardless, have you tried deleting and recreating the account on your iPhone over the last year?

I used the Gmail account preset with my old phone.  I just got a brand new 4S today and again used the preset and still got the "username/password incorrect" message when on cellular data.  It still works fine when on wifi. 

When you created the account, did you use the Gmail account preset or did you select Other followed by manually entering the incoming and outgoing server info?

Regardless, have you tried deleting and recreating the account on your iPhone over the last year?

You should use the exchange option for setup and then for server put in m.goole.com  Also I think that whne I set it up, was a while ago I had to go to m.google.com on safari to register my iphone.  With everything set up my calendar from google also syncs perfectly with my calendar app from gmail

I used the Gmail account preset with my old phone.  I just got a brand new 4S today and again used the preset and still got the "username/password incorrect" message when on cellular data.  It still works fine when on wifi.