Can somebody please help with this...do I need to change chmod of the JOOMSEF directory? In the CP it looks like the settings have been saved, but the url stays the same (I've tried different settings to test, but no changes at all to the url). Help please!

Dear Dajo, thanks for your instructions. It cut one bit of the problem.
Now the situation I'm experiencing is really annoying : I have my joomla 1.5 website running with Joomsef active and giving for example this path : www.montresdesign.com/videos/blog
In my new site (in pre production now) running joomla 2.5 and Joomsef the same content is displayed this way : www.montresdesign.fr/montres/videos
So as you can see, on the joomla 2.5, the structure is adding the category in the URL even if I set add categories url to no
And on joomla 1.5 the blog indication in the url is appearing while it's not the case in joomla 2.5

Thanks a lot for your help

cmswiz: After you change the settings, you need to use JoomSEF's URLs Manager to either delete or update already created SEF URLs, so they can be recreated with the new settings. Also make sure to clear Joomla's and JoomSEF's caches if you use them.

Montresdesign: Make sure that you also have the "Add menu title to URL" option disabled to remove the "montres" part. The "blog" part depends on the structure of the original non-SEF URL, Joomla 2.5 generates URLs differently than 1.5, so you will probably need to add the "blog" part by manually editing the URLs or set up 301 redirects.

Dear Dajo, I can't find the option "Add menu title to URL" vcan you tell me where it is ?
Thanks

I've just found it in the Extensions Management / Common but it's already set to No :(

I even tried to set it to Yes and it has no effect on the URL structure ...