In Outook 2007 I am getting an error Server was unable to proces the request -> The session ID is invalid at ...GetSessionUserID. soap.asmx line 553 ...Get_User_id  .. soap.asmx.cs line 819

When it does work if I log in to the site then Outlook will start throwing this error. Then if I restart the application pool it will work again until I login to the site.

I am going to try running it through the debugger but I wanted to see if anyone had seen this before and knew what may be causing it.

That is interesting.  Thanks for the feedback.