I've noticed in all of Sandboxes which have been upgraded to Summer '12, I'm now having a problem with my Visualforce email templates which use custom components. Whenever the components are rendered, I get something like the following:

<span id="j_id0:emailTemplate:j_id3:j_id4:j_id42">
COMPONENT CONTENT HERE</span>

This happens with all components, not just one. And as I mentioned before, it only happens in my Summer '12 sandboxes. My production instances and all my sandboxes that have not yet been upgraded are still fine.

Has anyone else seen this? Does anyone have ideas for a workaround?