Formatting oddity: ul tags when displayed in preview

I've noticed an oddity with the display of a posting I made last night. The post contains a ul tag which in preview is breaking, but which looks fine in full display.

My first thought was that the Read More module I'm using was causing problems because I had it using a series of three &lt's. That turned out not to be the case, though. Changing the link to not use &lt did not resolve the problem.

The issue appears to be limited to this particular post, which seems to rule out conflicts with input filters (I thought perhaps there was a conflict between the Markdown Syntax filter and Drupal's standard html processing). It seems like there must be something specific to the content of this post causing the issue, but I'm not seeing it at the moment.

Other work beckons, so I'll have to leave it as it for now.

[edit: 2009-07-06 09:12]
Well, I was wrong. It was the Markdown filter. Removing it from the processing steps for the input format I'm using resolved the issue. Guess the lesson here is don't mix your input formats.