Recently, I upgraded to a brand, spanking-new Dell Latitude D830 (a fantastic machine thus far, by the way!).  It came preloaded with applications, as vendors tended to do until Dell (in early July) announced its Vostro line, which enables you to "opt out" of all that garbage.  Anyway, the D830 came preloaded with applications (all of which I like) including Google Desktop, which I'd not used since upgrading to Vista Beta 1 with the integrated Windows Desktop Search.

I installed OUTLOOK 2007 (and the rest of Office 2007) on my laptop and immediately began getting error messages on Outlook startup: "Microsoft Office Outlook; A data file did not close properly the last time it was used and is being checked for problems. Performance might be affected while the check is in progress."  It happened every time, or almost every time, I started Outlook.  I was concerned about possible corruption to my mail, of course, so I began troubleshooting.  I've fixed these erros before, but this experience reminded me that it would be worth documenting for you, the Microsoft Office community. 

 So here's the bottom line: GOOGLE DESKTOP OUTLOOK TOOLBAR (GDOT).  Disabling it, restarting Outlook (several times) and reenabling it fixed it.

Here are the details:

IT IS ALMOST ALWAYS GOING TO BE AN ADD-IN THAT GIVES YOU THIS PROBLEM

As you close Outlook, add-ins don't always gracefully "let go" of the data files.

The first step in troubleshooting this error is make sure OUTLOOK itself is closing properly.  If it's not, then Outlook is the culprit.  Open Outllok then open Task Manager (CTRL+SHIFT+ESC) and click the PROCESSES tab.  Look for outlook.exe.  Exit Outlook and watch that the process does, in fact, disappear.  Then re-open Outlook.  Do you get the "Data file" error?  If you get the error, and outlook DID close completely, that's a sign that it's likely an addin.

Next, open Outlook 2007 and go to Addins:

1. Choose Tools > Trust Center
2. In the drop-down list at the bottom of the dialog box, choose COM Addins and click the Go button.

Test your add-ins one at a time (I recommend GDOT first, since that was the culprit in this example). Disable one.  Exit Outlook (making sure the process is cleared in Task Manager).  Reopen.  If you still get the error, reenable that addin and disable another.  Repeat until you find the offending addin.

In my case, it was GOOGLE DESKTOP OUTLOOK TOOLBAR.  Interestingly, it appears that just by disabling it (which stopped the error!) then re-enabling it later fixed the problem.

That reminded me about what is different about this computer versus my previous build.  First, my previous build didn't have GDOT (sign #1) and the previous build worked perfectly.  Second, this computer had GDOT installed FIRST, THEN Outlook 2007 was installed.  Perhaps that is a clue.  Especially since disabling, restarting Outlook, then reenabling seems to have fixed it.

That leads me to another lesson I've learned: Always install MS Office early in your "build" so that Add-ins are added and are added correctly.  Lots of applications hook into Outlook and other Office apps: Adobe Acrobat, Mind Manager, Snag-It, Camtasia, Google Desktop Search, and so many others.  I've run into several situations where removing apps that "hook in" to Office, then re-installiing them, fixed the problem.

A bit more detail, in case it helps you.  My full experience in this particular troubleshooting exercise, in detail, was:

1. Disable GDOT
2. Exit Outlook
3. Restart
• No Error
4. Exit Outlook
5. Restart
• Got a warning that "Outlook encountered problems with GDOT. Do you want to disable the Addin?"  Interesting... I HAD disabled it!... but I clicked YES to disable it.  Figured if Outlook still thought it was having issues, I should agree with Outlook.  Glad I did.
6. Outlook continued starting
• No Error
7. Exit Outlook
8. Restart
• No problem
9. Reenable GDOT
10. Exit Outlook
11. Restart.
• No problem.  seems to be fixed!

Hope this helps some folks!!