cubase 7 stopping while opening a cubase 6 project

I have a problem while upgrading from cubase 6 to cubase 7

I have run the upgrade on a Mac (OS X version 10.6.8) and the most recent update
I also entered the activation code

When I start the program, it starts up, when using an empty template.

However, when I try to open an older (cubase 6)project, it starts loading the files , but on a certain moment - while loading the mixer- it stops suddenly. In a dialog screen i am told that Cubase ‘has stopped unexpectedly’. I then have the choice between ignoring (which ends cubase), or start again, (that only starts the same loop again)

NB: the e- licencer tells me I have “cubase 7’ so that’s ok.

Can anyone tell me how to deal with this? I want to continue with my projects…

Trash Prefs.