Finally got it working on DNN5.0.

You need to make two small changes in SiteMap.aspx.vb to make it valid

on line 82 replace

Dim sb As New StringBuilder(1024)

on

Dim sb As New System.IO.MemoryStream

and on line 116 you need to change

Return sb.ToString

to

Return Encoding.UTF8.GetString(sb.ToArray())

you can check updated sitemap at www.lotteryuniverse.com/sitemap.aspx

IE shows it correctly now and http://www.validome.org/google/validate validated it as well.

Still waiting when google approves it though.

Hi -...  I'm using 5.0.1 and noticed that Google was throwing up an error about the SiteMap.aspx file:

Invalid XML attribute
The XML attribute of this tag was not recognized. Please fix it and resubmit.

I did a search and found this thread which gave me hope!  Unfortunately it looks like things have changed in 5.0.1 as the lines you refered  to I couldn't find in the SiteMap.aspx.vb file.

I checked my SiteMap.aspx in Firefox and this was the offending line:
<urlset xsi:schemaLocation="http://www.sitemaps.org/schemas/sitemap/0.9" url="http://www.sitemaps.org/schemas/sitemap/0.9/sitemap.xsd">

on your sitemap, which works, it is:
<urlset xsi:schemaLocation="http://www.sitemaps.org/schemas/sitemap/0.9 http://www.sitemaps.org/schemas/sitemap/0.9/sitemap.xsd">

So went in to my SiteMap.aspx.vb file and changed this:

writer.WriteAttributeString("xsi", "schemaLocation", Nothing, "http://www.sitemaps.org/schemas/sitemap/0.9")
writer.WriteAttributeString("", "url", Nothing, "http://www.sitemaps.org/schemas/sitemap/0.9/sitemap.xsd")

to this:

writer.WriteAttributeString("xsi", "schemaLocation", Nothing, "http://www.sitemaps.org/schemas/sitemap/0.9 http://www.sitemaps.org/schemas/sitemap/0.9/sitemap.xsd")

It now validates and seems to work fine with Google.  Not sure if this will be useful to others!