I am a new user of 1Password for iOS. I found a forum post from August 12, 2011 by "Gib Hoxie" which seems to exactly describe my issue getting started with 1Password for iOS. To quote that post:
"Yesterday's update of the iPad to iOS 4.3.4 (8K2) caused my previously working login to Schwab's accounts to fail.
1) The login information is correct.
2) Pressing the login arrow takes me to the correct URL and the necessary fields are filled in correctly.
3) When I press the "Login" button, the button "flashes" normally, but no progress happens in the URL window."
...except that the behavior is not due to an iOS update; it is what I see on first use. I can manually login on my iPad using Safari. If I do exactly the same login procedure through the 1Password browser, it fails. I am using the 1Password keychain synced from my Mac, where it works. I am running iOS 6.0.1.
I couldn't tell from that previous forum thread if there was a resolution.