>I must admit I asked this question in another place since I found this question to be very interesting. Here is an answer from the great SQL Server expert George Mastros:

This is a very detailed explanation on the issue. It confirms what I thought. This is also the recommended approach by many members on this site. Sergey mentioned it and since I have switched to the EXISTS, I haven't seen the error. I will wait for another week to make sure this has resolved the issue for good. But, based on that explanations, it all makes sense now. Thanks