Unknown Error...

I wrote a program that creates a list of all your files from a specified location. It works fine until I add alot of file. I used 'Program Files' to test this. It runs for a bit, and it gives me an Error that I've never seen or worked with before. And I don't know what causing it...

First, there's a MessageBox: "No Sysmbols are Loaded for any call stack frame. The source code could not be displayed."

Then after pressing the OK Button, Visual Studio shows me this:
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ContextSwitchDeadlock was detected

Message: The CLR has been unable to transition from
COM context 0x1b2520 to COM context 0x1b2690 for 60 seconds.
The thread that owns the destination context/apartment is most
ikely either doing a non pumping wait or processing a very
long running operation without pumping Windows messages.
This situation generally has a negative performance impact
and may even lead to the application becoming non responsive
or memory usage accumulating continually over time. To avoid
this problem, all single threaded apartment (STA) threads should
use pumping wait primitives (such as CoWaitForMultipleHandles)
and routinely pump messages during long running operations.
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I am still new to C# .Net and I would really appreciate it if someone could help.
:)