COM, .tli problem

Hi all,

I think have a problem with a COM object. I know nothing about COM
programming, the libraries it came with an OEM instrument that I am
using, and suddenly started generating errors in parts of code I've
never touched (MFC, .NET 2003).

My software uses a nanopositioner that my comp commutates with through
RS232. The nanopositioner (named "E816" - just to make the names make
sense) came with a COM library, so I import it like this:

#import "E816_COM\E816_COM.dll" no_namespace named_guids

Then communication with RS232 is initiated like this (from the
nanopositioner's manual):

CoInitialize(NULL);
HRESULT hr = CoCreateInstance(CLSID_E816, NULL,
CLSCTX_INPROC,IID_IE816, (void **)&e816_pointer);
long connectionTest = e816_pointer->ConnectRS232(1,115200);//3==COM3

Everything worked fine until I installed my program on a colleague's
comp. When attempting to connect to RS232 it generates an unhandled
exception which leads to this portion of a .tli file located in the /
debug directory:

inline long IE816::ConnectRS232 ( long nPortNr, long nBaud ) {
    long _result = 0;
    HRESULT _hr = raw_ConnectRS232(nPortNr, nBaud, &_result);
    if (FAILED(_hr)) _com_issue_errorex(_hr, this, __uuidof(this));
    return _result;
}

What is this .tli file? Can you help me pinpoint the source of the
problem? The problematic comp is in another state, so I need to guide
my friend over the phone to fix this.