JohnMu at Google has posted a thread announcement at Google Webmaster Help discussions stating there is an issue with some folks who might be trying to verify their sites with Google Webmaster Tools. Specifically, if you are trying to use the meta-tag verification method, you may currently be unable to verify your site with webmaster tools.

Dozens of reports came into the forum on Friday. So John posted an official thread and wrote:

There has currently not been an update that confirms things are working again.

Hopefully, you are not impacted.

Forum discussion at Google Webmaster Help.

Update: This is now resolved.