Paragraph formatting was there yesterday, gone today!

I'm lost on where and how $node->body and $node->teaser incoporate the formatting of lines & paragraphs. Somewhere in the last 24 hrs, my module has gone from normal line & paragraph formatting to absolutely none. All lines are merged into one block of text.
So far I can't figure it out where/how I've broken it, so if anyone has suggestions or pointers I'd be most grateful.