Totally feel the bees on that.
Whenever I need to completely switch gears from one project to the next (like going from Drupal into Zend Framework), I will require at least two weeks of downtime (although I would never dare admit to it to my manager). It's unavoidable. It's like my brain is jammed between channels and no matter how much I beat the horse, it will be this way while my neurons rearrange themselves. Then, one sunny day, bing it's all realigned and reprogrammed and I'm off to the productive races.
Wish there were medical-creative downtime available....