Have you tried just calling the mms APN "MMS" same as the telstraclear one is? Obviously keep the rest of the 2d settings.. It was the only way I could get my android phone to send one. (btw, I'm on telstraclear so there's no guarantee this will work, but it's worth a crack. Make sure mobile data is enabled too)
I've had the same problem. I could send pxt on Vodafone with the Desire but since going 2D no variants of apn settings have worked. I believe I read the issue with Desires not pxting on 2D is a known issue but there seems to be no fix at this point.
My partner had this issue on VF. Had entered and checked the setting more that onece. Problem cured by going into the main (VFNZ) APN settings --> Last Field is APN Type. this should be: default, supl where as fone setting had: default. supl (note the comma not a fullstop)