[ZendTo] Verification fails

[shuttlebox]

I have just installed ZendTo via the VM image (CentOS). It seemed to
work including dropping off files anonymously via the captcha (old
Google) registration.

Then I upgraded the whole system via yum upgrade that got me ZendTo
4.12-5 and checked the configs for any changes. Now the captcha (new
Google) seems to work but when I click the "Send confirmation" button
it just stalls and continues with:

You did not complete the form, or you failed the "Am I A Real Person?" test.

I filled in the three lines with name, org and e-mail and got a green
checkmark from the Google captcha.

If I login with a local account everything still seems to work but I
need this anonymous thing too.

Any ideas?

/peter