API - Read Only with Basic Authentication?

Hi, When making calls to http://api.openstreetmap.org/api/0.6/ to update elements I am getting a "405 (Method not allowed)" response. I could swear it was working a week or so ago...

The Basic Authentication itself seems to be working - if I use a dummy user name and/or password I get a 401 Unauthorized. With the same authentication I can get the permissions using /api/0.6/permissions and they are all there. But when I go to do an actual update (opening and closing the changeset is working fine) I get the "405 (Method not allowed)". I am using PUT (as per the documentation) but I have tried using POST - same results. The response includes this header: "Allow: GET, HEAD, OPTIONS".

Using https instead of http gives the same result, so I am sticking with http for the moment for ease of debugging (with Wireshark.)

Using the same account with Potlatch has no problems - but that uses OAuth instead of Basic Auth.

Am I doing something wrong? Has updating via Basic Auth been turned off deliberately? Any ideas?

A bit background - this is how I issue requests to the server:

I am working in VB.Net using HttpWebRequest
Typical url is http://api.openstreetmap.org/api/0.6/relation/12345, using PUT, with XML payload
Basic Authentication being added like this:
                Dim cre As String = $"{Credentials.UserName}:{Credentials.Password}"
                Dim bytes As Byte() = System.Text.Encoding.ASCII.GetBytes(cre)
                Dim base64 As String = Convert.ToBase64String(bytes)
                req.Headers.Add(“Authorization”, “Basic ” + base64)
Payload written like this:
                Dim b() As Byte
                b = System.Text.Encoding.UTF8.GetBytes(sPayload)
                req.ContentLength = b.Length
                req.ContentType = "application/xml; charset=utf-8"
                With req.GetRequestStream
                    .Write(b, 0, b.Length)
                    .Close()
                End With