I get this error when reading some data from an SQL column then converting it to XML:
\"System.InvalidOperationException: There is an error in XML document (182, 16
Have you tried nchar(0x0B)
instead of char(0x0B)
yet? As it sounds like your dodgy character is Unicode.
Character 0x0B
cannot be used in an XML document (see the list of valid XML characters here.) Please consider migrating invalid XML characters like this to valid XML (e.g. the sequence 
).
Finally found it !
The .NET XML serializer was escaping the invalid character when serializing it, but then it was un-escaping it before de-serialization.
So I had to search for the escaped  to find the un-escaped 0x0B ... seriously not funny guys!
So this:
SELECT * from Mytable where Column like '%' + '' + '%'
Will actually find this:
<?xml version="1.0"?>
<Hashtable><key>313_other_10</key><value></value></Hashtable>
And while this looks like valid XML it will throw an invalid character exception when :
XmlSerializer xs = new XmlSerializer(Type.GetType(Hashtable));
StringReader stringReader = new StringReader(xml);
obj = xs.Deserialize(stringReader);
Many thanks to people who jumped in to help! It was unvaluable help!