One of the thing I hate most about Sharepoint is its naming. It does not tell the administrator what name it's actually storing a column field of, and this could always lead to errors. One way to find out is to do a column filter on the all items display page. This will show the actual fieldname in the url. One thing to note is that spaces in column names will get converted to "_x0020_" which will be shown as "%5f" in the url. So, if you ever want to use it in code, replace "%5f" with "_x0020_".
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