Error calling Outlook 2010 macros from Excel 2010

I recently upgraded from 2007 to 2010 and the following code snippets no longer work:

Sub excel_test()
    Set OL = CreateObject("Outlook.Application")
    OL.outlook_test ' <---- ERROR HERE
End Sub

and

Sub outlook_test()
    MsgBox "Hello, world!"
End Sub

The first snippet is in an Excel module. The second is in Outook ThisOutlookSession.

This USED TO WORK - as is - until I upgraded.

Now, I get an error on the noted line: Run-time error '438': Object doesn't support this property or method.

I have tried everything I can think of, and everything I could find online (very little). Thank you in advance for your assistance.