Category from main menu - template lost [solved]

I've downloaded the trial version and I've only one issue (so far   )

when I click on a link in the main menu that shows a all articles in a category all the template formatting is lost.

SEF Advance 2008 trial version
Joomla 1.5.10
Template Joomlashack JSSimplicity
website: www.money-magnets.net

That's the only link that caused me problems (well the same thing happened with Xmap but I just excluded that).

Any ideas what could be causing this?

Thanks,
Karen  

I was looking for a way to remove the index.php that appears and saw an answer on another thread that mentioned

'Yes, you must enable "Use Apache mod_rewrite" in global configurations.'

and when I did that this problem vanished so I guess it had something to do with that.

I have to say this seems pretty quick and simple after spending all day trying (and failing to get a competitor to work).