Is there a list of COM error codes somewhere?
From Standard COM Errors (at least for Microsoft Commerce Server):
The following table shows the most common standard COM errors returned by the properties and methods of the Commerce Server objects:
Constant Value (32-bit) Description S_OK 00000000 The standard return value used to communicate successful completion. S_FALSE 00000001 An alternate success value, typically used to communicate successful, but non-standard completion. The precise meaning depends on the method or property in question. E_UNEXPECTED 8000FFFF Catastrophic failure error. E_NOTIMPL 80004001 Not implemented error. E_OUTOFMEMORY 8007000E Out of memory error. E_INVALIDARG 80070057 One or more arguments are not valid error. E_NOINTERFACE 80004002 Interface not supported error. E_POINTER 80004003 Pointer not valid error. E_HANDLE 80070006 Handle not valid error. E_ABORT 80004004 Operation aborted error. E_FAIL 80004005 Unspecified error. E_ACCESSDENIED 80070005 General access denied error.