I'm going to try and produce a reliable way of doing this, and post here, but I'm finding quite often line returns aren't saving properly with the wysywyg editor.
This was happening in Beta 3 as well.
What browser are you using?
I've worked out a way of repeating this.
I think there are other ways but here's one repeatable bug.
Enter some text for example test. Then finish the line with a double colon:
Then enter more text on the next line. Press post.
The line returns will disappear.
Edit: Actually sorry this appears to be a problem on Chrome.There is an issue with IE7, but I'm still unable to reliably reproduce it.