MSP2007 - Summary EV Calculation

First of all, apologies if this has been covered in a previous post - I have gone back 3 years on this board and not been able to find the answer!!

Using MSP2007, I have been asked to produce a fairly basic EV report, and thought that MSP would be the ideal tool to do this. There are a number of tasks that roll up under three separate summary bars (Design, Procurement, Construction). All tasks are baselined, and I have added some cost information against the tasks (fixed costs rather than labour rates x hours).

As I would have expected, if I progress tasks as all up to date, task SPI/CPI are coming out as 1.

When I enter % complete as less than the Planned Value information, the task shows the "shortfall" in cash terms, and also shows the SPI being less than 1 (as expected), but does not show this shortfall in "earned value" as a forecast overspend in the EAC field, nor does the CPI change as I would have expected.

In addition, when I check the summary tasks, this is showing an SPI of 1.94, rather than something between 0.83 and 1 (the two SPI values of the sub-tasks).

I have searched the internet for a solution, and whilst there seems to be an acknowledgement that this is a problem, and the suggested solution of changing the EV calculation basis to use "Physical % Complete" does not seem to make any difference.

Is there something glaringly obvious that I am missing here? Any help gratefully accepted!!