I am not surprised to hear this. Growing up in the South, and being in a technical field this is something that I work against every day. But...

They mentioned that this setting would affect whether the "NOT IN" would return the correct results or not. I will have to determine if they might have been talking...

We encountered this problem as well on a new install of Reporting Services.  Turned out that even though I had all the roles assigned that I was not a user...