Can anyone get me started on the above?

SEF advance running in a J1.5.26 site. I just checked the logs and see lots of 404 errors.

For example:

This is the Bad requested link (direct request):
http://artists-bill-of-rights.org/competition-lists/rights-off-list/vancouver-organizing-committee-for-the-2010-olympic-%2526-paralympic-winter-games,-gov,-canada/

This is the working SEF advance URL:
http://artists-bill-of-rights.org/competition-lists/rights-off-list/vancouver-organizing-committee-for-the-2010-olympic-and-paralympic-winter-games,-gov,-canada/

Bad requested URL:
http://artists-bill-of-rights.org/competition-lists/rights-off-list/weymouth-and-portland-borough-council,-%2523uk,-%2523gov/

Good SEF advance URL:
http://artists-bill-of-rights.org/competition-lists/rights-off-list/weymouth-and-portland-borough-council,-uk,-gov,/

Bad requested URL:
http://artists-bill-of-rights.org/about-us/about-us/what-can-you-do?%2F/

Good SEF advance URL:
http://artists-bill-of-rights.org/about-us/about-us/what-can-you-do/
(This had a question mark at the end and I removed it and created a redirect from any requests that had the question mark)

Requested Bad URL:
http://artists-bill-of-rights.org/news/campaign-news/pinterest-versus-ethics-and-the-law-%20-part-1/

Referred from:
http://translate.google.com/translate_p?client=tmpg&hl=en&langpair=en%7Cit&twu=1&u=http://artists-bill-of-rights.org/news/campaign-news/pinterest-versus-ethics-and-the-law-%2520-part-1/&usg=ALkJrhioPAcqJchBNNDvMI5uArDEEOI4dw

Good SEF advance URL:
http://artists-bill-of-rights.org/news/campaign-news/pinterest-versus-ethics-and-the-law-%11-part-1/

Even search engines are turning up 404s.

Can someone help me begin to sort this? Where are these bad requests coming from?

PHP     5.2.17
Joomla! 1.5.26
DB collation: utf8_general_ci

Obviously I'm in over my head.

The "modules/mod_ajaxrecommend/mod_ajaxrecommend.php" was set to 644 instead of 755. And I had a custom htaccess file that was excluding direct access to that file. After adjusting these, everything works.

Thanks, Saka.

Thanks, Saka.

I sent you an email.

Joomla 1.5.23, latest PHP, my admin emails work, and whether I set "From" to admin or user, I get "request failed".

I'm using jQuery and Mootools from Google (latest) via JB Library.

Any suggestions?

Here is the site, but I had to turn the AJAX module off because it is live.
http://artist-bill-of-rights.org/

I can add the module to an "unpublished" menu page if you need to see the problem.

Thanks!