[squid-users] Reverse Proxy to Exchange 2010 OWA slow load time

I am testing with Squid 3 Stable 13 on CentOS 5, reverse proxy to
Exchange 2010 and seeing very slow page on the main OWA page. When I
access OWA, the initial login page loads very quickly, then I click
"Sign In." The next screen takes 4-5 mins to finish loading. I sat there
and timed it... If I hit refresh 3-4 times, the page loads completely.

Once the OWA main page fully loads, browsing is normal. If I close my
browser and login in OWA again, speeds are normal. If I clear my
browser's cache, the problem returns. The issue does not happen if I
directly connect to OWA. I searched the archive email and saw someone
with the same exact issue, but there were no replies. Originally I had
Squid 2.6 stable 21, then I upgraded to 3 Stable 13, hoping that would
address the issue, but it did not.

Thanks for your time and help.

--
Here is my config:
visible_hostname devlinux1.domain.net
extension_methods RPC_IN_DATA RPC_OUT_DATA
https_port 443 cert=/etc/pki/cert/owa_domain_com.crt
key=/etc/pki/cert/owa_domain_com.key defaultsite=owa.domain.com
cache_peer 192.168.179.235 parent 443 0 no-query originserver login=PASS
ssl sslflags=DONT_VERIFY_PEER front-end-https=on name=owaserver
acl all src 0.0.0.0/0.0.0.0
acl owa dstdomain owa.domain.com
cache_peer_access owaserver allow owa
never_direct allow owa
http_access allow owa
http_access deny all
miss_access allow owa
miss_access deny all
cache_mem 256 MB
cache_dir ufs /var/spool/squid 1000 16 256
#maximum_object_size_in_memory 256 KB
minimum_object_size 0 KB
maximum_object_size 32 MB