As of WordPress 2.9.2, comments no longer work on future/scheduled posts.
This ticket modified wp-comments-post.php to no longer allow comments on future posts, among other post status'.
Is it possible to modify your plugin to allow comments on future posts again? We absolutely love your plugin and use it display our upcoming events, but not being able to comment on those posts is a huge bummer.
The only solution I have is to basically revert the patch for wp-comments-post.php and remove future posts from its validation. Modifying the core is not my ideal solution, but, being a designer, plugin development is beyond my skillset.
I'm hoping you can modify your plugin to make this work.