Custom htaccess for Joomla Site

Our website is run on Joomla 1.5.25 and recently we have been having some serious link issues. The notable and largest problem is that for some reason Google is indexing good URLs with /[login to view URL] between them. The core Joomla SEF is enabled and this site has been active for years without this problem. The second issue is that Google is crawling and indexing bad URLs as a result of combining good URLs. For example, good URLs are [login to view URL] and [login to view URL] We have found many bad URL combinations that would look like [login to view URL] It is my understanding that a correctly formatted htaccess file can be incredibly powerful and I am hoping to solve these problems with a new one. The completion of this project will entail: 1) Ensuring that the htaccess file is correctly formatted for Joomla SEF. The traditional mod_rewrite would apply. 2) Remove [login to view URL] from the equation for SEF links. 3) Solve the issue associated with bad URLs as a result of combining good URLs.