I’ve been following this thread (having same issues). None of the solutions above worked for me – tried it on both WP 3.3.1, and 3.4 (upgraded too soon). And even with the functions.php hack above, still getting errors. Upgraded to latest Tribe plugins, tried disabling most of plugins (including SEO), and still getting blank pages. Only if I disable permalinks, do these forms show up. And I cannot turn off that function. Please update when this issue is fixed for ‘permalinked’ WP sites.
In the meantime, does the ‘gravity forms’ solution still work?