I'm having a problem with Attachments in YAF editor. When the attachment icon is selected, the popup doesn't list existing attachments,, but shows "internal server error" above "upload new files". However, I can still upload and use new attachments.

It appears that the POST to …/forum/YafAjax.asmx/GetAttachments is giving HTTP 500 error; the detail of the error is
"System.InvalidOperationException: Request format is invalid: application/json; charset=utf-8.
at System.Web.Services.Protocols.HttpServerProtocol.ReadParameters()
at System.Web.Services.Protocols.WebServiceHandler.CoreProcessRequest()

The web service appears to be fine with XML requests, but is rejecting JSON requests.

What have I got wrong in my web.config?

YAF version 2.24.20

I should have googled a bit harder first!

I needed to add
<add name="ScriptHandlerFactory" verb="*" path="*.asmx" preCondition="integratedMode" type="System.Web.Script.Services.ScriptHandlerFactory, System.Web.Extensions, Version=3.5.0.0, Culture=neutral, PublicKeyToken=31BF3856AD364E35" />

to system.webserver.handlers