Solved - 2.1 RC4 - white screen when trying to edit resource in manager

everything looks normal until I try to edit a resource - then nothing, nada, snow storm at the north pole...

on my laptop running in MAMP - restored back to RC3 all is well, reinstalled (update) same problem.
Quick look around - other things are working in the manager

modx 2.1 rc4 traditional
Apache 2
php 5.2.13
mysql 5.1.44 server and client
pdo_mysql is installed
MAMP on OS 10.6.7

Safari 5.05/Chrome ?/Opera 11

you know it would be nice if it was easy to copy all this system info from the manager - maybe it is and just was hard because I’m trying to get out the door!

I just tried this again - and it worked on development laptop
What went wrong before? Who knows - I did not knowingly do anything different.
I will now try a hosted site!

edit: this also worked fine