So, you did a clean flash, and cannot install developer mode after that. I find that quite strange, as I just reflashed my device and there was no problems whatsoever.

Did your device work correctly after flashing? Did you manage to connect to wlan or gprs access point, as developer mode activation requires that yuou are able to download some packages to your device.

Can you please list in detail what did you do, what are the error messages and so on? (please start from the flashing, what binaries did you use and so on.)