Can't auto-login to captive portal wifi on iOS 5.1.1

My office uses a captive portal wifi system for non-work devices. On iOS 5.1, the OS would detect this and would pop up a browser window after connecting to the network for me to enter my login information. In addition, in the detailed wifi settings for the network, I would see two switches for enabling auto-join (connecting to the network) and auto-login (popping up the browser window).

After updating to iOS 5.1.1, on both my iPhone 4S and iPad (3rd gen) it no longer recognizes our network as a captive portal network. The extra settings are gone from the wifi settings, and the only way for me to join the network is to attempt to open a website in Safari and be redirected.

Can anyone else with access to a captive portal network confirm whether or not this issue occurs for them in 5.1.1?