An unhandled exception of type 'System.TypeInitializationException' occurred in System.dll

My visual basic application (targeting Framework 4) was running perfectly until I added code that was originally targeted for Framework 2.0 (specifically altering the column headers of a datagridview). The code executed without problem the first time (when debugging), and thereafter my application won't start. I deleted all the newly added code and debugged, but the errors stayed. I even loaded my backup into Visual Studio, but no change.

I get the following errors and have no idea where to find the source of this problem:

First-chance exception at 0x77cd708f in "app.name".exe: 0xC0000008: An invalid handle was specified. An unhandled exception of type 'System.TypeInitializationException' occurred in Sy开发者_如何学Gostem.dll. Additional information: The type initializer for 'System.Net.ComNetOS' threw an exception.

I re-installed Visual Studio and Framework 4. I googled the errors, but nothing pointed me to the location causing the error. I don't believe it's in my code, because I built in try/catch blocks from the very start of the code, even using application events 'startup' and 'unhandledexception', but the app doesn't even start that I may catch the exception stacktrace.

Visual Studio indicates that no symbols are loaded for call stack frame and no source is available. I'm not aware of an error log that might provide details.

Hope someone can help.

This should explain First Chance Exceptions. and how to debug the .dll that causes them