Thanks for the quick reply
The php environment is setup to allow 8GB. Joomla was using 12MB at the time.
As for the joomla debugging, thats how we found out the memory usage of joomla at the time. There were no real entries in the server error log that I know of, and well, a error 500 doesn't really allow you to display too much more... (unless i'm mistaken)
I've been scouring the phpinfo() data from my server (which it runs fine on) and my friends server (where we are getting the errors, and where we are trying to setup CB).
Would using the joomla "Install from web" vs downloading the package and installing from uploaded package have any effect?