[squid-users] page not being cached... is this right?

Hi,
I have installed squid 2.6stable14 (windows binary linked from the
site), and am getting a fair proportion of what should be cached
cached, but not the most important things!
I have deactivated the default setting to ignore urls with ? in it,
and am getting all those pages/images except this page with cache
hits. However, those have cache-expires headers and are cache-control
public... Am I missing something with the below headers that means it
won't be cached?
Thanks for your time!

http://www.mysite.test:3128/a/b/?nav_cat=128&lang=en_US

GET /a/b/?nav_cat=128&lang=en_US HTTP/1.1
Host: www.mysite.test:3128
User-Agent: Mozilla/5.0 (Windows; U; Windows NT 5.1; fr; rv:1.8.1.6)
Gecko/20070725 Firefox/2.0.0.6
Accept: text/xml,application/xml,application/xhtml+xml,text/html;q=0.9,text/plain;q=0.8,image/png,*/*;q=0.5
Accept-Language: fr,en;q=0.8,fr-fr;q=0.5,en-us;q=0.3
Accept-Encoding: gzip,deflate
Accept-Charset: UTF-8,*
Keep-Alive: 300
Connection: keep-alive
Cookie: prtl_2048=2052; prtl_2048=2052;
__utmz=196985131.1183130363.1.1.utmccn=(direct)|utmcsr=(direct)|utmcmd=(none);
__utmb=196985131;
__utma=196985131.1319757679.1183130363.1186756561.1186757873.6;
JSESSIONID=82F28C32D70FD2B8E87CF5F93F3B392A; __utmc=196985131

HTTP/1.x 200 OK
Server: Apache-Coyote/1.1
Set-Cookie: prtl_2048=2052; Expires=Sat, 11-Aug-2007 00:58:16 GMT
Content-Type: text/html;charset=UTF-8
Date: Fri, 10 Aug 2007 14:58:20 GMT
X-Cache: MISS from pc-am.siege.ours.local
X-Cache-Lookup: MISS from pc-am.siege.ours.local:3128
Via: 1.0 pc-am.siege.ours.local:3128 (squid/2.6.STABLE14)
Connection: close
----------------------------------------------------------

store.log
1186757048.978 RELEASE -1 FFFFFFFF ED746D4F06EEF75757282B4CA0B25510
200 1186757048 -1 -1 text/html -1/42930 GET
http://www.mysite.test/a/b/?

access.log
1186757998.370 5032 127.0.0.1 TCP_MISS/200 43227 GET
http://www.mysite.test/a/b/? - FIRST_UP_PARENT/server_1 text/html
Received on Fri Aug 10 2007 - 09:22:43 MDT