[squid-users] TCP_MISS/999

Dear friends,

I'm having odd problem of getting TCP_MISS/999 in access.log whenever a
yahoo dynamic content webpage (mail/myyahoo/profile/calendar etc) is
accessed. Whenever user try loggig in using username and password,
following message is returned IMMEDIATELY:

--
Unfortunately, we are unable to process your request at this time. We
apologize for the inconvenience. Please try again later. 
Return to Yahoo! 
--
Title of this error message page is: "Yahoo! - 999 This page is
currently unavailable"
I get the same error message even if the password for a specific user is
incorrect. Means yahoo server doesn't bother about what username I'm
talking about...
I get the following error in access.log:
--
1072853196.666    947 xxx.xxx.xxx.xxx TCP_MISS/999 1408 GET
http://login.yahoo.com/config/login? - DIRECT/216.109.127.60 text/html
--
IMP: I'm running squid in transparent mode and if I bypass proxy, yahoo
sites work just OK for all users.
I'm running 2.5.STABLE4 on Redhat 8 (2.4.18-14smp).
configure options:  --prefix=/opt/squid --sysconfdir=/etc/squid
--enable-storeio=ufs,diskd --enable-removal-policies=lru,heap
--enable-snmp --enable-cache-digests --enable-poll
--enable-linux-netfilter --enable-truncate --enable-underscores
--enable-cache-digests
Any suggestion???
--
Shiraz Malik