MDX statement (subcube, calculated measure) throws strange exception

Hello

I've got a problem with a MDX-statement on SSAS 2008.
To describe the problem, I have created an equivalent MDX query for Adventure Work database:

with member [Measures].[SalesMinusTax] as
  [Measures].[Internet Sales Amount] - [Measures].[Internet Tax Amount]
select
  {
      [Measures].[Internet Sales Amount]
     ,[Measures].[Internet Tax Amount]
     ,[Measures].[SalesMinusTax]
  }
  on 0,
  non empty
   [Product].[Product].members
   *
   [Product].[Model Name].members
 on 1
from 
(
  select
   [Product].[Model Name].&[All-Purpose Bike Stand]
  on 0
  from [Adventure Works]
)

--> Exception

This query returns an error message which is (on my machine) unfortunately in german:
"Fehler bei der MDX-Funktion '', da die Koordinate für das Model Name-Attribut eine Menge enthält."

This can be translated by:
"Exception in MDX function '', because the coordinate for the Model Name attribut contains a set"

No exception is thrown when I comment out the calculated measure:

with member [Measures].[SalesMinusTax] as
  [Measures].[Internet Sales Amount] - [Measures].[Internet Tax Amount]
select
  {
      [Measures].[Internet Sales Amount]
     ,[Measures].[Internet Tax Amount]
     //,[Measures].[SalesMinusTax]
  }
  on 0,
  non empty
   [Product].[Product].members
   *
   [Product].[Model Name].members
 on 1
from 
(
  select
   [Product].[Model Name].&[All-Purpose Bike Stand]
  on 0
  from [Adventure Works]
)

--> No Exception

There is also no error if the statement contains the calulcated measure but no subquery:

with member [Measures].[SalesMinusTax] as
  [Measures].[Internet Sales Amount] - [Measures].[Internet Tax Amount]
select
  {
      [Measures].[Internet Sales Amount]
     ,[Measures].[Internet Tax Amount]
     ,[Measures].[SalesMinusTax]
  }
  on 0,
  non empty
   [Product].[Product].members
   *
   [Product].[Model Name].members
 on 1
from  [Adventure Works]

--> No Exception

What causes the problem?
Why is the statement which contains both the subcube and the calculated measure not correct?

Thanks a lot
Saxeten