Odd Permalink problem???

Hi people,

I’m new here *waves*, trying to change my permalinks to ‘http://bandtshirts.org.uk/category/post-name/’ on my site however when I press save an extra / comes in on before anything that I can’t seem to get ride of plus the links go to a not found page? Any ideas? Think I m using the latest version of WP.

Thanks,

Tawny