Comment on WordPress Menu Manager Stallion Theme Feature by WordPress SEO Theme Author.
The above error is due to running an old version of WordPress, get_post_format() was added in WordPress 3.1 and Stallion uses the latest WordPress code. So your site must be running WordPress 3.0.* or earlier.
If you update to the latest version of WordPress the error will be gone.
I develop Stallion so it works in the latest two major versions of WordPress. Currently WordPress is at version 3.3.* so I’m checking Stallion works in WordPress 3.2.* and WordPress 3.3.* (it also works in WordPress 3.1.*, but if something broke in WordPress 3.1.* I wouldn’t fix it unless it was a simple fix).
When WordPress updates to WordPress 3.4 I’ll check WordPress 3.3 and WordPress 3.4 when working on updates. I’ve checked Stallion 7.1 with WordPress 3.4 beta releases and early release candidates and already updated some code in the current Stallion version.
More Comments by WordPress SEO Theme Author