Serial IO: CreateFile & CloseHandle in managed class

[Steve N.]

I'm looking to do some basic (to begin with anyway) Serial IO in a __gc
class. I use this code open a port:

m_hSerialComm = CreateFile(LpstrPort, GENERIC_READ|GENERIC_WRITE, 0, 0,
OPEN_EXISTING, FILE_FLAG_NO_BUFFERING, 0);

I was able to write successfully, but the following code hangs:

if(m_hSerialComm != INVALID_HANDLE_VALUE) {
CloseHandle(m_hSerialComm);
m_hSerialComm = INVALID_HANDLE_VALUE;
}

Looking at m_hSerialComm in the debugger states that its value is
'{void}'. My only guess is that the problem stems from being within a
managed class... any help?

Steve