XSLT browser issues

Hello and thank you for your great work!!!
 
I have a question regarding the following namespace:
 
http://www.w3.org/1999/XSL/Transform <http://www.w3.org/1999/XSL/Transform> 
 
When I use this, it works fine in MSIEv.6.0(Japanese), but in my own
browser, which MSIEv.5.50, it will not quite utilize thew powerful features
of XSLT, so I have had to change the namespace (and sacrifice functionality)
to:
 
http://www.w3.org/TR/WD-xsl <http://www.w3.org/TR/WD-xsl> 
 
What am I doing wrong?  Is the former namespace (
http://www.w3.org/1999/XSL/Transform <http://www.w3.org/1999/XSL/Transform>
) incompatible with MSIE5.5?
 
I hope you can help me resolve this and again, I appreciate your work
 
Repsectfully,

Michael A. Norton 
Technical Writer 
OM USA Corp. 
(310) 325-0040 Ext. 285