Programatically Generate Well-Formed XML with .NET

I hope this isn't too far off topic...

I'm using VBA to write a file with a .xml extension on to my
harddrive.  Basically, I'm using the Range.Text method in Excel VBA as
the selector and a stream output method to write out a text file.  The
problem is that it is not consistently writing well-formed XML.  After
running my crummy program, a browser often chokes on the result with

"Whitespace is not allowed at this location. Error processing resource
'file:///C:/Saxon/bin/mySkus.xml'. Line 58, Position..."

here is a copy/paste of my line 58.
<sku quantity="1" description="XMediusFAX Express Server 50 Users & 2
Channels *Server Supplied by Benchmark">XM-EXP-50</sku>

I don't see anything wrong with it?  I've tried using VBA's
StrConv(string, conversion) where the conversion is set to VBUnicode
but that just adds spaces to all my text and makes matters worse.

Is there a way to ensure that my xmlWriter subroutine creates
well-formed XML?  Maybe I should be using something from the MSXML
library instead?

Thank you.

- Ronnie Royston