I have the same kind of problem :
As admin with moodle (1.3.2) on localhost, I have create 3 disciplines and each has 1 course.
I could not go back to administration for none of these courses and neither to enrol students...
Tonight I create a new course in one of the discipline and it was possible to modify settings students, teachers in the bottom back menu admin. But for the course create before still not.
I thought it might came from the begin date of the course ( in order not ot modifiy it after it is open...) but I made the test in creating the new one and it does not matter.
If anyone has an new idea for this...
Bye for now.
Anyway what a nice program! thanks.