"An object was not found"

Does anyone out there have information on the following Outlook error message: "The operation failed. An object was not found"

I have 2 Dell machines. I worked fine with Outlook, the second has never worked...always displaying the above error message. Now, after reloading the OS (XP) and all apps on the first machine, I am getting the same error message

My ISP says they have heard of this error, and that it is a known bug in Outlook, but because they do not support MS, they do not have a fix

Thanks in advance....