s2Member completely blocks admin pages

[alerttopia]

Hi all,

I just upgraded to WP v3.1, downloaded latest s2member plugin (v3.5.1), pro (v1.5.1), pro extras (v1.5.1), s2clean (1.2.5).

Updated the s2clean theme without problems. The install of s2member (v3.5.1) goes without any problems. However when I active the plugin, I immediately receive a pop-up (screen shot attached) asking me to open a php file in an application of my choice. Any link on in the admin section stops working and displays the pop-up. To gain control of the admin screens again, I have to SSH into my server and remove the plugin directory.

I have disabled all other plug-ins. I have tried to active s2member plug-in with or without pro add-on, without luck. Both options result in the pop-up to display, rendering the backend useless.

Unfortunately there are no error messages displayed.

Also, when I close the browser and proceed to the login screen, which displays fine, after login I am presented with a complete blank page.

The plug-in used to work just fine before upgrading in my environment.

Any thoughts?