MDX query across multiple Role-Playing Dimensions in SSAS 2008R2

Here is what I would consider to be a magic post:  http://richardlees.blogspot.com/2011/06/linkmember.html

Mr. Lees does the Lord's work here, and surely helped me out of a jam.  I was trying to figure out a way to collect a single measure across multiple role-playing dimensions.   Everything I tried was epic fail, including the solution I initially arrived at which was to create 3 separate queries and let SSRS sort them out....

To set the scene, an example of the problem I was having would be:
- I want to find the numbers of New Widgets, Sold Widgets, and Improper Widgets, by month over the last 12 months (Rolling 12 Month totals).
- In my SSAS cube I have a Measure for Widget Count, and I have 3 role-playing Date dimensions -- Released Date, Sale Date, Inspection Failed Date -- all based on a single Date dimension living in the underlying Data Mart.
- Appropriately filtering and slicing the Widget Count by any of the above dates yields correct results.  But since the cube believes (techically properly, I guess) that those role-playing dimensions are all actually different dimensions, I cannot get a good slicer Axis out of only one of the date dimensions.  So, in a nutshell

In other words, I couldn't get into a single query/dataset all 3 of the desired measures. This was because I really needed to query a single measure across 3 different role-playing dimensions.

So, in comes Mr. Lees.  He introduced me to the magic of LinkMember().  And thus I quickly solved my problem.   LinkMember allowed me to create a Calculated Member that gave me totals aligned with each of the Role Playing Dimensions I was looking at.  Booyah, granny!

RDL won't open in Design View in BIDS 2008? No problem.

You may find yourself working on an SSRS report in BIDS 2008. You may ask yourself, "Why can't I re-open this report in Design View?  Why is it this ugly line of non-formatted HTML?"

You may also find yourself behind the wheel of a large automobile, or living in a beautiful house, with a beautiful wife. But that's neither here nor there...

I have had this problem multiple times, and every time I have to look up the answer on the MS SQL Server forums.  But today, they were down for maintenance, so I was up the creek.  Therefore, I decided that once I refound the answer, I'd blog it, and provide links and a summary explanation. 

This puts it in a nutshell, and is where I eventually find the answer (usually).  So credit where credit's due:  http://blog.hoegaerden.be/2009/03/28/the-datatype-attribute-is-not-declared/

And here's a brief explanation:

There is a (known) issue within BIDS 2008 where it will serialize a Report Parameter's XML incorrectly.   If your report has an Available or Default value, BIDS will add an attribute called "DataType" in to one or more of your parameter's Value tags.  This effectively invalidates the entire RDL, because the Value tag doesn't actually have that attribute.  You try to open an RDL in Design View that's been saved this way, and the deserializer can't do it.  Ka-boom.  You receive a long horizontal scroll of unformatted HTML.  Yay.

The solution is:
Simply delete those attributes where they are found. 
Do a Find on "<Value DataType=" in the HTML and delete the attribute (and its value) wherever it turns up.

Hope this is helpful.  Now that I've written this out, I will expect myself to remember it....