You "Resolved" Other Topic With the same title even though the issue was not resolved. So let try again:
With the recent upgrade to v1.8.6 a simple snippet shortcode began insert '<p>' and '</p>' and the beginning and end of rendered result.
I have tried all the options in the "Fix AutoP filter:" setting and none of them fix the issue.
For an example check out http://samplesite2.optimized-marketing.com/ the Phone number and hours in the header as well as the word "Massachusetts" at the bottom of the page and it the footer are all shortcodes and all have <p> tags around them in the source code. The code I am entering into the shortcode HTML section is just text (No Html markup or anything special) with the ShortCode Type: Simple Snippet.
I am using Genesis Themes with the Venture Child Theme on this site. It also is happening on a different Child Theme.
WP version 3.4.2