Header domain-level cookies not being saved in IE6 or IE7

We have a web site running on Apache 2.0.53. We are trying to set a
cookie for Unica NetTracker through the header, but IE6 and 7 are not
accepting it. It is accepted in Firefox just fine.

Here is how the two cookies on the site are being set:

Set-Cookie: SaneID=69.59.180.231-1194465308907482; path=/;
domain=.ourdomain.com\r\n
Set-Cookie: JSESSIONID=5067F8B1A0A96745B0A9D69B670D60DE.p2; Path=/\r\n

Note that the second one is always set successfully, but the first one
(the SaneID) is not. Further, if we remove the
"domain=.ourdomain.com" parameter from the SaneID cookie it saves
just fine in all browsers.

A bit more info that may be helpful: The cookies are being written to
the username@www.ourdomain.com cookie file as opposed to the
username@ourdomain.com file. I'm not sure if that is part of the
problem (we are also running Google Analytics, and although those
cookies are set by JavaScript, they are also domain-level cookies and
save just fine, but they save to the username@ourdomain.com cookie,
not www.)

Finally, I tried accessing our site at just http://ourdomain.com
instead of http://www.ourdomain.com to see if the issue had something
to do with the hostname. The second cookie (the JSESSIONID) was now
being written to username@ourdomain.com, but the Sane cookie still was
not.

We have consulted with Unica NetTracker and they have no idea, saying
that this cookie works for all their other customers. Any ideas?
Thanks!