MDX Query Running very slow after adding a new dimension

Hi,

I have made some changes to an existing MDX query that was running just fine through a reporting services interface,  and it now seems to be taking over an hour and a half to return the correct data.

I have included the MDX query below. Highlighted in bold is the new line I added which seems to cause the query to run slowly.

For information there is a relationship between Delivery Agent and Delivery Agent Type dimensions through a foreign key.

Any help or pointers as to what the issue might be would be greatly appreciated.

Kind Regards,

Juee

SELECT NON EMPTY { 
[Measures].[Item Charges Count], 
[Measures].[Cost Price], 
[Measures].[Cost Price Advanced Element] 
} 
ON COLUMNS,  { 
(
[Delivery Agent Type].[Agent Type Key].[Agent Type Key].ALLMEMBERS * 
[Delivery Agent Type].[Agent Type Description].[Agent Type Description].ALLMEMBERS * 
[Delivery Agent].[Agent Description].[Agent Description].ALLMEMBERS * 
[Dim Access Type].[Access Type].[Access Type].ALLMEMBERS * 
[Dim Line Item].[Line Item Description].[Line Item Description].ALLMEMBERS * 
[Dim Line Item].[Line Item Charge Type].[Line Item Charge Type].ALLMEMBERS 
) 
}DIMENSION PROPERTIES MEMBER_CAPTION, 
MEMBER_UNIQUE_NAME ON ROWS FROM 
( SELECT 
( 
{ [Dim Charge State].[Charge State Description].&[Initial state prior to billing], 
 [Dim Charge State].[Charge State Description].&[Unmediated], 
 [Dim Charge State].[Charge State Description].&[Mediated], 
 [Dim Charge State].[Charge State Description].&[Unrated - No chargeband], 
 [Dim Charge State].[Charge State Description].&[Rated - Chargeband set], 
 [Dim Charge State].[Charge State Description].&[Unrated - No Tariff], 
 [Dim Charge State].[Charge State Description].&[Billable to agent], 
 [Dim Charge State].[Charge State Description].&[Not billable to agent] 
} 
) ON COLUMNS FROM 
( SELECT 
( 
STRTOSET('[Billable Month].[Month].&[2012-12-01T00:00:00]', 
CONSTRAINED) ) ON COLUMNS 
FROM 
( SELECT( STRTOSET('[Dim Source].[Source Name].[All]', CONSTRAINED) ) 
ON COLUMNS FROM [Generic Rental Billing DW]))) 
WHERE ( IIF( STRTOSET('[Dim Source].[Source Name].[All]', CONSTRAINED).Count = 1, 
STRTOSET('[Dim Source].[Source Name].[All]', CONSTRAINED), 
[Dim Source].[Source Description].currentmember ), 
IIF( STRTOSET('[Billable Month].[Month].&[2012-12-01T00:00:00]', 
CONSTRAINED).Count = 1, 
STRTOSET('[Billable Month].[Month].&[2012-12-01T00:00:00]', CONSTRAINED), 
[Supplier Billable Month].[Month Name].currentmember ), 
[Dim Charge State].[Charge State Description].CurrentMember ) 
CELL PROPERTIES VALUE, 
BACK_COLOR, 
FORE_COLOR, 
FORMATTED_VALUE, 
FORMAT_STRING, 
FONT_NAME, 
FONT_SIZE, 
FONT_FLAGS