Shared Datasource Connection String Keeps Getting Wiped Out

I originally reported this on the TechNet site, but one of the moderators asked me to post here. Here's the link to that thread: http://social.technet.microsoft.com/Forums/en-US/sqlreportingservices/thread/a4c54e10-3d59-4d30-8264-bfc250b4cfbe

I have a report that has a main report query based off an OLAP cube. It also uses a shared datasource for other queries. There are times when I make a seemingly innocuous change to the report, like adding a border to a table cell, and when I go to preview the change, the report comes back to tell me:

[rsInvalidReportDefinition] The report definition is not valid. Details: The report definition element 'ConnectionProperties' is empty at line 13, position 9. It is missing a mandatory child element of type 'DataProvider'.
Build complete -- 1 errors, 0 warnings

I then have to go into the Datasource Properties window, just opening it and then hitting "OK" to close it again, to reinstate the connection string (even though it shows properly when I open the dialog box). The kicker is that it seems totally random. Sometimes the small change will require this action and other times it doesn't. Version information can be found on the TechNet posting... Thanks in advance for you help.

John