After I updated one server today from Debian Lenny to Squeeze, puppetd stopped to work and printed the following error:

sgssr240003:~# puppetd --server  --test --ca_port 8141
warning: peer certificate won't be verified in this SSL session
err: Could not request certificate: Error 405 on SERVER: Method Not Allowed
Exiting; failed to retrieve certificate and watiforcert is disabled

I was a bit confused and did not find useful hints regarding that error message. In the IRC channel #puppet I was told that this can happen, if the puppet client (puppetd) is newer than the puppetmaster.

And indeed, when I compared the versions, puppetmasterd was running version 0.24.8, whereas puppetd was 0.25.1.

After I upgraded puppetmasterd to 0.25.1, it is runs fine again.

If you also have been running into this problem, the article is for you!

Update #1

I switched over to use cdist instead of Puppet.