Dataset Designer: Unable to find connection MyConn (MySettings)1 for object ‘MySettings’

Solved:
http://social.msdn.microsoft.com/Forums/en-US/winformsdatacontrols/thread/08a48cad-619d-4421-b584-f2b5550ba6c5

Solution from Don,
“I had the same problem with one of my projects. If you open up the Dataset using the XML editor you should see a line near the top that looks like this:

<DataSourceDefaultConnectionIndex=“1“FunctionsComponentName=“QueriesTableAdapter“Modifier=“AutoLayout, AnsiClass, Class, Public“SchemaSerializationMode=“IncludeSchema“xmlns=“urn:schemas-microsoft-com:xml-msdatasource“>

I changed the DefaultConnection Index from a 1 to a 0 and the problem went away. I suspect at one time I had two connections and one went away but the index was not updated.

<DataSourceDefaultConnectionIndex=“0“FunctionsComponentName=“QueriesTableAdapter“Modifier=“AutoLayout, AnsiClass, Class, Public“SchemaSerializationMode=“IncludeSchema“xmlns=“urn:schemas-microsoft-com:xml-msdatasource“>”

Also other posts here may be useful:
In my particular case had too many connection strings and deleted one of them.