well, I was just curious if there were any differences in the installation procedure.
*To run a nightly you should use the unstable recovery. To run a normal release, you should use stable recovery.
*You need to install gapps AFTER you've installed CM.
When you flash CM7 on an install which already runs CM7, I believe you are doing an upgrade. Possibly even after you've wiped all caches you're still stuck with the upgrade. Now, you could try to go back to your stock rom and do an official sbf upgrade through "motorola software update". Make sure all google apps work correctly, if not, try installing them. Only when they are working, then try installing CM7. You will not need to flash another sbf (nordic, etc.) before flashing CM7, the official froyo is enough.