pagespeed cache exp problem

[dethfire]

I have this in my htaccess which is in my root www folder.

# Turn on Expires and set default to 0
ExpiresActive On
ExpiresDefault A0

# Set up caching on media files for 1 year (forever?)
<FilesMatch "\.(ico|flv|pdf|mov|mp3|wmv|ppt)$">
ExpiresDefault A29030400
Header append Cache-Control "public"
</FilesMatch>

# Set up caching on media files for 1 week
<FilesMatch "\.(gif|jpg|jpeg|png|swf|js)$">
ExpiresDefault A604800
Header append Cache-Control "public, proxy-revalidate"
</FilesMatch>

# Set up 2 Hour caching on commonly updated files
<FilesMatch "\.(xml|txt|html|css|rss)$">
ExpiresDefault A7200
Header append Cache-Control "private, proxy-revalidate, must-revalidate"
</FilesMatch>

# Force no caching for dynamic files
<FilesMatch "\.(php|cgi|pl|htm)$">
ExpiresDefault A0
Header set Cache-Control "no-cache, no-store, must-revalidate, max-age=0, proxy-revalidate, no-transform"
Header set Pragma "no-cache"
</FilesMatch>

If I check my main page http://www.physicsforums.com with pagespeed it says almost all my items are cached. Good! However if I check a page link http://www.physicsforums.com/forumdisplay.php?f=149 then it says none are cache. What am I doing wrong? thanks!