String not working in my menu

Hello,
I've read the FAQ and did search on the forum unsuccessfully.
I've joomla 1.5.17 , SEF 2.3 and jreviews 2.1.23.
I've menu item pointing to jreviews categories. I've added in the strings: jreviews=>opiniones but I'm still getting a /jreviews/ in the URL corresponding of my menu.
i've checked and I have sef_ext.php in my jreviews component folder.
Did I forget anything?
Thanks

If you done everything right it should work. If not, send the access info so I can check.

Fixed. The pairs must be separated by comma, not just new line. And I emptied the page cache.