404 Page Not Found

WordPress version: 3.4.2
Optin Revolution version: 1.0.8

I did this:

– Installed Optin Revolution version 1.0.8
– Configured Optin Popup 1 Settings for MailChimp
– U: XXXXXX (entered correctly as instructed)
– id: XXXXXX (entered correctly as instructed)
– Action: sumofallmoments.us6.list-manage1.com
– Customized & configured pop form, shows up on my homepage perfectly, enter email address and click “sign me up” button and the am taken to “404: Page Not Found” with the following message on the page:

“MailChimp
It seems the page you were looking for has disappeared

We’ve recorded this vanishing act and our team of chimp magicians will find the missing link.
Return to the Dashboard”

– I have tripple-checked with MailChimp and all is fine on their end and I have tripple-checked my Optin settings and all appears as it should.

Any suggestions?

http://wordpress.org/extend/plugins/optin-revolution/