Man, after spending days digging, I finally found the problem.
Gavick News Show Pro GK5 is causing the 1064...
Disabling it seems to solve the problem.
For others who might have this problem, here's the link to the thread with the solution (from Joomla Works, the makers of K2)
www.joomlaworks.net/forum/k2-en/43295-er...on-user-pages#148164
Thanks Alex & Melissa!