Line breaks

I have recently switched from Joomla to WordPress v2.8.5, using Firefox v3.5.3 and the theme Plainscape 1.0.3 by Srini G. The site is on https://www.nevadabase.co.uk

I cannot place line breaks into my post! I have tried hitting enter, shift+enter and editing the HTML. I then installed the FCKEditor but this did not help.

I read another thread that describes some hacks but none of these seem to completely solve the problem and, more to the point, a hack to make a new line?!

Please let me know if there is anything I can try to solve this.

Thanks a lot,

Albert