I enabled security debug, cleared the log, went to the pages app, created the error a few times but nothing was logged to the security debug.
The 403 is probably being thrown client side which is why we can't get any logs. I have tried IE and Chrome so it doesn't appear to be browser specific.
I have also reset the macro signatures using the existing hash salt value. I din't want to change the salt unless we absolutely needed to.
Next I am going to see if I can back up the db and restore it on another machine but we only have the 1 dev server so it will be on a laptop not the same server OS.