I have installed MailChipm plugin 1.2.9 on WP 3.4.1 (latest). Got the API from MailChimp, selected the right list and updated the Subscrive Form Settings.
At the bottom below the Interest Groups a line shows up saying:
Error retrieving interest groups. Please re-import the list.
I have re-imported the list into MailChimp. There was one untitled field which I deleted manually via MailChimp Field page, so now the list seems to look OK - also on the WP side, identifuing the 4 correct fields (email, first and last name, and Email Type (i.e. Home or Work).
But that error seems to remain.
In searching it here it appears in a page that shows the widget's code - but I don't know how to fix the problem. Any ideas...?