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In Visual Studio 2010, I had to go to Tools\Options\Debugging\Just-In-Time and uncheck "Managed"|

f:\dd\ndp\fx\src\... is the path to the source file on the machine that the .Net Framework was compiled on.

Go to Tools, Options, Debugging, Symbols, and select Only specified modules.
Also, uncheck Enable source server support in Debugging/General.

Go to Tools, Options, Debugging, Symbols and select Only specified modules.
It worked for me.