I found an odd bug in the .NET framework v1.1.  I don't have room to load v2.0 on my drive.  Can someone tell me whether this bug exists in v2.0?  The bug test is a simple VB console app:

Module EntryPoint
Sub Main()
Dim x0 As Xml.XmlDocument = New Xml.XmlDocument
Dim xr As Xml.XmlTextReader = New Xml.XmlTextReader("..\EntityTest.xml")
Dim xv As Xml.XmlValidatingReader = New Xml.XmlValidatingReader(xr)
Try
x0.Load(xv)
Console.Error.WriteLine("Value [copy]: {0}", x0.DocumentType.Entities.GetNamedItem("copy").InnerText)
Console.Error.WriteLine("Value [lt]: {0}", x0.DocumentType.Entities.GetNamedItem("lt").InnerText) ' Throws System.InvalidOperationException
 Catch ex As Exception
Console.Error.WriteLine("Error: {0}", ex.Message)
Console.Error.WriteLine("Value [lt]: {0}", x0.DocumentType.Entities.GetNamedItem("lt").InnerText) ' Returns empty string!!
End Try
End Sub
End Module

This produces an exception about the state of the object, yet the state seems to be fine where it pulled the text of the copy entity. Worst, if you trap the .GetNamedItem("lt").InnerText and execute it again, it doesn't throw an error but return a zero length string!!
 
The xml file (EntityTest.xml) validates just fine with a variety of xml parsers:
<?xml version="1.0" encoding="utf-8" ?> 
<!DOCTYPE doc
[
<!ENTITY nbsp "&#160;">
<!ENTITY copy "&#169;">
<!ENTITY lt "&#38;#60;">
<!ENTITY gt "&#38;#62;">
<!ELEMENT doc (#PCDATA)>
]
>
<doc>&lt;&copy;&gt;</doc>

Thanks, Grumpy.