Making MS stable

Joel,
I know how to do it, and it is easy to do but not so easy to explain in one sentence, especially without being able to see your file and without knowing exactly what it is that you are doing and what you hope to achieve when you "update the schedule and re-schedule".
I have some notes and examples that I have written up about this and could send them to you, or I could put them here (but it is a lot of text). You can email me at:
trevorATperfectproject.com.au

MS Project works with the equation:
Work = Units * Duration

It has (from grade school math) 3 forms:
W=U*D U=W/D D=W/U

Project has 3 task types:
Fixed Work; Fixed Units; Fixed Duration.

Work = Units * Duration
12 = 4 * 3

Change Work to 24. What should Project do? Change Units to 8 or change Duration to 6?

Look at the task Type field. You are changing Work; which of the other two do you want to hold constant?

If you set the task Type to Fixed Units then Project will hold Units at 4 and when you change Work to 24 then Project will recalcuate Duration to 6.

If you set the task Type to Fixed Duration then Project will hold Duration at 3 and when you change Work to 24 then the Project will recalculate Units to 8.

It is, as you can see, very simple and straight forward.

The default options for New Task Type and Effort Driven can be set up to be of Fixed Duration and Not Effort Driven under Options Menu, Schedule Tab.

For tasks already defined, for easier editing on a Table View insert columns for “Type” and “Effort Driven” fields. Here you can use fill down for any continuous range you want to edit.

If you can make MS Project stable as P3 then, congratulations!