htaccess problems, image problems

It seems the only issue I have left from the upgrade to 3.0 is that none of the images are showing. I have tried most if not every suggested fix I see in the other posts and not one of them worked.

I seem to have an .htaccess issue too. First off I can’t get an FTP program to work on this computer. I had FileZilla on my PC, but it went down some time ago and I am now on a laptop. So, instead I have been going through my cPanel which doesn’t allow me to actually see the .htaccess file. I can see the htaccess.txt file though. What I have been doing is saving a file with the code I want and then copying it as .htaccess . It is making the changes because if I put the following code in it and save as .htaccess the site loads (with no images)
RewriteEngine On
RewriteBase /

#uploaded files
RewriteRule ^(.*/)?files/$ index.php [L]
#RewriteCond %{REQUEST_URI} !.*wp-content/plugins.*
#RewriteRule ^(.*/)?files/(.*) wp-includes/ms-files.php?file=$2 [L]

# add a trailing slash to /wp-admin
RewriteCond %{REQUEST_URI} ^.*/wp-admin$
RewriteRule ^(.+)$ $1/ [R=301,L]

RewriteCond %{REQUEST_FILENAME} -f [OR]
RewriteCond %{REQUEST_FILENAME} -d
RewriteRule . – [L]
RewriteRule ^([_0-9a-zA-Z-]+/)?(wp-.*) $2 [L]
RewriteRule ^([_0-9a-zA-Z-]+/)?(.*\.php)$ $2 [L]
RewriteRule . index.php [L]

However, if I add ANYTHING beyond that above code the site will not load at all.

The only other things in the htaccess.txt file are the ANTISPAM code, the WPSuperCache code, and the following code at the end.

<IfModule mod_security.c>
SecFilterEngine Off
SecFilterScanPOST Off
</IfModule>

If I try to add any of that it kills the site.

Any ideas out there?
What should be the code in the .htaccess file besides the above?