I'm not sure exactly where the issue lies, but I thought I'd report the issue anyway. When using this plugin, in combination with the Register IP - Multiste plugin, the IP Address column displays, but none of the IP Addresses show up.
I can use your plugin to show/hide the IP Address column, but even when it is shown, the column is created, the column heading exists, but the IP Addresses, are hidden.
If I disable the Codepress Admin Columns the IP Addresses will re-appear again.
I have reported this issue in the Register IP - Multiste plugin's support area as well.