The current implementation of transient caching always looks for the post ID when the_content filter is applied. This ends up causing problems when the_content filter is applied to other text that is displayed on a page along with the post content.

janw.oostendorp proposed using a hash of the content being filtered instead of the post ID. I think this sounds like a pretty good solution.
http://wordpress.org/support/topic/cache-is-breaking-my-site?replies=2