What exactly is the prompt and is it exactly the same both times? The way I read your post it could be [TBL_USMD Server List].OS or [Enter OS here].
You might have misspelled a table or field name and haven't even noticed the effect of that on the query results. In that case, you can get prompted for every reference to the misspelled word.
Also, you're not using wildcards for several of the LIKE operations so there's not much point to it. I would use Not In('mike', 'kyle', 'john', 'etc.')
The more we hear silence, the more we begin to think about our value in this universe.
Paraphrase of Professor Brian Cox.