xml sitemap ----Sitemap is HTML

I used the seositemap in xml to submit to google and it worked properly for about 4 days but my webmaster daskboard just alerted me that it stopped reading it with this response.

Sitemap is HTML
Your Sitemap appears to be an HTML page. Please use a supported sitemap format instead.

The sitemap is in xml and I donot understand why it suddenly recognizes it as an html sitemap.

Does anybody know what the isssue would be and is there a solution.

Thanks, Blake

Sorry for the post.. wow. forgot I closed the store for maintenance. No problem to begin with reads fine

I have 2 issues.

1. If I try and submit */sitemap.xml I get this error: "
This is not a valid URL. Please correct it and resubmit." and

2. If I load */sitemap then I get the error: "Your Sitemap appears to be an HTML page. Please use a supported sitemap format instead.

Can you please advise how to resolve this issue.

You need to submit your full URL:
http://www.yourdomain.com/sitemap.xml

I have submitted the full URL but I still have the issue

Please respond with the URL you are submitting to them so that I can confirm. Or you can try validating your XML file using http://www.xmlvalidation.com/

I'm guessing that some strange character is in your feed that is causing malformed XML syntax..