So I woke up this morning and Outlook had crashed on me. Every time I'd try to restart Outlook, I'd get the same crash error—even rebooting didn't help. The error was in the ntdll.dll.
I figured maybe there as something in my POP3 account that Outlook was having problems reading, so I snagged a tool to allow me to read the headers and delete messages. In my POP3 account were some messages with some Shift-J encoding—so I thought for sure that was the cause of the crash. However, even after deleting those messages I was still getting crashes.
After over an hour of troubleshooting, I was getting pretty frustrated. I figured at this point it was either some Windows Update that installed itself or a add-on causing the issue.
The primary add-on I run is Cloudmark—which is a spam filtering tool. I decided to head on over to their Community Forums to see if anyone else was having this problem. Sure enough it seems like most Cloudmark users started experiencing the problem some time last night.
After reading through several more complicated solutions, I found one that was very straightforward and worked for me--just renaming the \Documents and Settings\[Profile Name]\Local Settings\Application Data\Cloudmark. Here are the instructions from WildBill
In Vista, go to C:\Users\[Profile Name]\AppData\Local\ and rename the Cloudmark folder to Cloudmark.bad.
In XP, go to C:\Documents and Settings\[Profile Name]\Local Settings\Application Data\Cloudmark and rename the Cloudmark folder to Cloudmark.bad.
Then start up Outlook and you're good to go. You do not need to uninstall or reinstall Cloudmark.
In order to preserve your whitelist settings, you'll want to copy 2 files over from the old directory to the new directory.
Those steps worked for me. So if you're having problems getting Outlook to work and you're running the Cloudmark Spam Filter tool, try these steps to see if Outlook starts working again. It worked great for me.