XML TASK XSL Variable: Exception 'Property New Source Has No Source Xml Text'

Hi,
I want to transform an xml flow to an html flow. For this, I create an XmlDataDocument, I add on it, all that I want, and I store it in a file (in a dataflow task).
After that, in an xml task, I set the input properties like that:
Operation type: xslt
SourceType: File connection
Source: ras.xml
 
All works fine. But now, I want to use a variable to store my xml data. So, instead of storing my data in ras.xml, I store it in a variable like that:
 
Dim v As Microsoft.SqlServer.Dts.Runtime.Wrapper.IDTSVariables90
Me.VariableDispenser.LockOneForWrite("RAS", v)
v("RAS").Value = doc.OuterXml
v.Unlock()
 
and in the xml task, I set configuration like that:
 
Operation type: xslt
SourceType: Variable
Source: user::RAS
 
But when I execute, I got this following exception:
 
Error: 0xC002F304 at Format HTML Mail, XML Task: An error occurred with the following error message: "Root element is missing.".
Error: 0xC002928F at Format HTML Mail, XML Task: Property "New Source" has no source Xml text; Xml Text is either invalid, null or empty string.
 
Furthermore, when I want to debug it, in replacing the xml task, by a script task, I can see that in my RAS variable, I get the xml data which is well formed.
 
<?xml version="1.0" encoding="UTF-8"?>
<root> €¦
</root>
 
(When I store it in a file, I can see it in IE)
 
Have you got an idea ?