As far as I know, a fully updated N1 won't have any exploitable vulnerabilities to allow you to root the device. Most of the older "one click" and similar methods used things like Gingerbreak, which were holes in Android that eventually got patched. I have not seen a root exploit on vanilla Android since Gingerbreak.
XDA's wiki has a couple of different options regarding the N1 which work but require unlocking the bootloader, and unlocking will perform a factory reset automatically. They can be found here and basically amount to:
- Unlock the bootloader from fastboot mode with
fastboot oem unlock
- Flash a custom recovery (usually ClockworkMod)
- Flash a zip file from recovery that will install
su and Superuser for you