CPU Hangs on Deserialize

[Reg]

OK, Here is the issue:

I have a string of XML that has been validated against the XSD.

This XSD also created a class called XMLRequest (using xsd.exe).

When I attempt the following code, my CPU is zooming to near 100%
(aspnet_wp) eventually the request times out.

---------
XmlSerializer xs;
MemoryStream memoryStream ;
XmlTextWriter xmlTextWriter ;

xs = new XmlSerializer(typeof(XMLRequest));
memoryStream = new MemoryStream(xmlutil.StringToUTF8ByteArray(xmlfile ));
xmlTextWriter = new XmlTextWriter(memoryStream, Encoding.UTF8);

//CODE DIES HERE
XMLRequest xRequest=(XMLRequest)xs.Deserialize(memoryStream);
//CODE DIES HERE
---------

Any ideas what may be causing this? My XML/XSD is fairly straigtforward,
only ever nests to 2 deep at the max.

Are there certain structures or other wise I should avoid? Or perhaps a
better method for doing this.

Thanks for Reading!

Reg