While browsing the CF Forums today, I found out that another Duplicate bug exists. This is a bit sad as Duplicate() has had issues in the past and I thought it was "perfect" now (ignoring the fact that it breaks on CFCs). It looks like you should carefully consider what you are duplicating now until a hotfix is (hopefully!) released. The following example demonstrates the bug:
<cfset s2 = StructNew()>
<cfset s2.numb = 12>
<cfset s2.string = "hello2">
<cfdump var="#s2#" label="s2 struct">
<p>
<cfset s = StructNew()>
<cfset s.array = ArrayNew(1)>
<cfset s.array[1] = 22>
<cfset s.array[2] = "my array">
<cfset s.array[3] = Duplicate(s2)>
<cfset s.numb = 11>
<cfset s.string = "hello">
<cfdump var="#s#" label="S struct">
<p>
<cfset s3 = Duplicate(s)>
<cfdump var="#s3#" label="S3 struct - duplicate from S">
<p>
<cfset StructDelete(s3.array[3],"numb")>
<cfdump var="#s3#" label="s3 after deleting s3.array[3].numb">
<p>
<cfdump var="#s#" label="S struct after deleting from S3 (deleted s3.array[3].numb)">
<cfset s2.numb = 12>
<cfset s2.string = "hello2">
<cfdump var="#s2#" label="s2 struct">
<p>
<cfset s = StructNew()>
<cfset s.array = ArrayNew(1)>
<cfset s.array[1] = 22>
<cfset s.array[2] = "my array">
<cfset s.array[3] = Duplicate(s2)>
<cfset s.numb = 11>
<cfset s.string = "hello">
<cfdump var="#s#" label="S struct">
<p>
<cfset s3 = Duplicate(s)>
<cfdump var="#s3#" label="S3 struct - duplicate from S">
<p>
<cfset StructDelete(s3.array[3],"numb")>
<cfdump var="#s3#" label="s3 after deleting s3.array[3].numb">
<p>
<cfdump var="#s#" label="S struct after deleting from S3 (deleted s3.array[3].numb)">