That's precisely why disable-output-escaping is such a bad idea - it only works when the output is being directly serialized, which isn't the case when writing to a variable.
Show us why you are using d-o-e, and we'll try to find a way of getting the same result "properly".
Michael Kay
http://www.saxonica.com/
Author, XSLT 2.0 and XPath 2.0 Programmer's Reference