If there are no new posts since your last visit, you will get 'Sorry - no matches'.
How many new posts does it say there are for you once you've signed in on the homepage?
If it's more than zero, you should get some results.
What is the reported last-visit timestamp?
Also, tell us what you get for these two links :
http://www.satellites.co.uk/php-bin/forum/search.php?do=getnew
and
http://www.satellites.co.uk/php-bin/forum/search.php?do=getdaily
The second one should return a few pages of posts.
The first is the same command as 'New Posts' and the second gets the last 24 hours posts.
If you get nothing back, it's almost certainly cookie related, but may be a corrupt database entry for your username. To prove that to yourself, try from a different computer, or a different browser.