There are dozens of reports in the Google Webmaster Verification Help section from disgruntled webmasters where they cannot verify their web sites with Google Webmaster Tools.
Jonathan Simon and other Googlers are replying to webmasters that this is a bug and will be fixed soon. In one Google Webmaster Help thread, Jonathan said:
Our verification service has been experiencing intermittent issues today. Please retry verifying your site and post back here if you're still seeing the same error message.
And Dennis G. from Google said in another Google Webmaster Help thread:
Sorry, we had some server trouble this morning. Service should be returning to normal now.
I hope this is resolved soon, if not already.
Forum discussion at Google Webmaster Verification Help.

Comments:
r keller
03/27/2010 04:28 am
I am facing same problem.
No Name
03/30/2010 07:52 am
This could also be because in Webmaster Tools they only show: meta name="google-site-verification" For the meta data verification, without the content 'code'. Admittedly the content name is hidden within the 'link', but it's still pretty poor for Google.
maurice cooper
11/19/2010 12:30 pm
yeah