Using Access 2002 latest sp.

I've got a pivot chart based on the following query:

SELECT Production.Date, [Weight]/1000 AS Kg, Production.TimeHrs AS Hrs, [Weight]/[TimeHrs] AS KgHrs, Production.Machine
FROM Production
WHERE (((Production.Date) Between [From: (d/m/yy)] And [To: (d/m/yy)]) AND ((Production.Machine)=[forms]![ProductionReports].[Machine]) AND ((Production.PlanType) Is Null));

This pulls total weight / total hours worked / average kg/hour for a selected machine. I can get a bar chart showing with a bar for each of these three sitting next to each other no problem. When I select total hours and make this a line graph, then take av.kg/hr and make this a line graph it still works ok and this is how I want it (ie total weight as bars, total hrs and kg/hr as lines, all showing on same graph).

However when I select a different machine the graph reformats itself to a bar graph again, with total weight, total hrs + kg/hr showing as blocks. When I select my original machine the formatting is still there as I want it.
When I select a different machine and it reformats back to bar graph, if I manually format it again to show two line graphs and one block graph it's then fine for this machine, but the original machine has now gone back to a complete bar graph!!

The pivot chart is basically not keeping 2 line plots and 1 bar plot on the same graph when you change to a different input criteria.

Can someone please assist on this, I need these up and running asap for "the boss".

thanks