I didn’t see this doc­u­mented any­where, but you have to cre­ate the fol­low­ing MIME types on your web server when you move to HTTP updates as your transport.

IS Man­ager -> <your server> -> Default Web Site -> Your Direc­tory -> properties.

Go to http header -> MIME Types. Add

.m25 application/binary (for v10)
.x86 application/binary (for v8 & v9)