Hello,
I've a problem with Artio JoomSEF 1.5.1

the url's look good, but after installing the www. in the browser is disabled

that means, I type my address:

www.mechanix.info
and I get:
mechanix.info/ >without www. in front

after installing JoomSEF my Googleranking is complete down, before my site was on search page 1 and now we are on 5 or 6 by using the most interesting search word...

Is this because the www. is missing or is it another problem?

That also happened to me. It's due to that www. is missing! It takes a couple of week until Google recognise the new URL's. And then it works fine.