D threading and shared variables

[Archie Allison via Digitalmars-d-learn]

I have written an industrial control program which uses serial 
ports to communicate with hardware but am having problems, 
perhaps with shared memory, on Windows.

The SerialPort class calls C object-file functions. Transmits are 
on one thread and receives on another (all within a class derived 
from Thread), with a signal(created from a mutex) notifying the 
transmit thread when a packet has arrived.

This generally works OK when tied to a Console but when link 
options are changed to be SUBSYSTEM:WINDOWS and 
ENTRY:mainCRTStartup it rarely does.

Compiling with -vtls shows the serial port is in thread local 
storage. As a hardware resource, I wasn't sure if this matters. 
I've tried casting to a shared object so it no longer appears in 
the -vtls list, with no difference.

Does anyone have ideas about where I may have misunderstood the 
threading and shared-memory design of D or what I can look at?