Using blog clients such as BlogJet or Windows Live Writer with Drupal can produce some unwanted things, such as ignoring the perex/article break or curious formatting. There is very simple module to solve.

Someone says at Drupal pages:
(…) WLW's "split post" feature, which is available when using the Movable Type API but not with the Metaweblog API, does not produce the <!--break--> tags that Drupal expects. Instead it produces <!--pagebreak--> sometimes and <!--extended--> other times, despite the fact that before posting, the HTML source within WLW shows <!--more-->. Supporting all of these possible page-breaking tags in Drupal would require hacking the core.
BlogApi: post from blog tools | drupal.org
I’ve extended the module from this discussion and rewrite it for Drupal 5 too. Updated module can convert P and BR tags to NL.
You can download it here:

Attachment	Date	Size
blogapi_break_converter_5.zip	14/12/08 9:20 am	884 bytes
blogapi_break_converter.zip	14/12/08 9:18 am	892 bytes