Blockify causes WSOD with CTools and Zen theme

I'm not sure the exact culprit here, but using Blockify has resulted in a white screen of death on all pages of our site!

I enabled the current version of Blockify, and then went to its admin page and chose to show Tabs as a block. Then I enabled the Tabs block on all pages on the left sidebar. Upon saving, I get a WSOD on all pages with the following error:

Fatal error: Call to undefined function ctools_menu_primary_local_tasks() in /pathtodrupalfolder/pressflow/sites/somatics.org/themes/zen/zen/template.php on line 103

So, I don't know if this is a problem with...
1) Blockify,
2) CTools, or
3) the Zen theme.

All I know is that I have all 3 running and I had 2 & 3 running very smoothly until I enabled Blockify and the Tabs block.

All three items are running with current release version, according to their Drupal pages and according to our Available Updates page.

We would very much like to use the Tabs as a block function asap, so we hope there's an answer to this.