Invalid XML tag - Google Webmaster Tools - Warning - Error

[Leandro]

I been already searching for a solution for this problem since a long time ago...
I have found many people having the same issue and no one found a solution to it.

In my particular case, the Xmap plugin v2.2.1 (latest version) using Joomla 1.6.3 its working fine, i am able to create and publish site map on my back end.

My problems started when i tried to submit the site map in Google webmaster tools and I do a test to the site map.

http://www.co-production.net/index.php?option=com_xmap&view=xml&tmpl=component&id=8

I get the following WARNING

Warnings - Invalid XML tag - This tag was not recognized. Please fix it and resubmit.

130 issues found - example:
Parent tag: url
Tag: uid

this is a piece of my site map

<url><loc>http://www.co-production.net/</loc><uid>com_contentc77</uid><itemid>464</itemid><changefreq>weekly</changefreq><priority>0.5</priority></url>

Test #1
If i disable the extension Xmap - Content Plugin the issues in Google go down to 36, but it only submits 18 pages from 65 that i got originally submitted...

I really like to use this plugin and Donate money for it's use, but this issue with Google it's stopping me to go ahead and send you some collaboration and continuing using this wonderful tool.

Can you please take 5 minutes of your life and at least ell me what should I do, or if you can or can't help me?

thank you

NOTE: I found this article in Google http://www.seroundtable.com/archives/020215.html