http://www.petri.co.il/ie7_crashes_when_opening_esm_help.htm
Start here.
1. In adsiedit first verify if your PF tree is a MAPI PF tree and not a
general purpose tree.
ADSIEDIT.MSC Click Ok. (ADSIEDIT is part of your Windows 2000\2003
Support Tools found on the CD)
Expand the Configuration Container.
CN=Services
CN=Microsoft Exchange
CN=Your Exchange Org
CN=Administrative Group
CN=First Administrative Group
Highlight CN=Folder Hierarchies.
On the right pane, highlight CN=Public Folders and select properties.
Scroll down to find the attribute, msExchPFTreeType. For the value,
check if it is set. If not set, set to 1.
2. Second verify that your PF store is associated to this tree.
This time search for the attribute msexchowningpftreebl and double
click it. Do you see the DN of the PF store of your server? Also do you
see any servers\stores that do not exist or are unmounted?
3. Verify step 1 in this article.
http://support.microsoft.com/kb/842273/en-us
James Chong
