Hi,
Also try with different combination of virtual and physical (real) COM port speed. For example if you want to test serial link at 2400 b/s use virtual 2400b/s and physical 9600b/s.
When you use Proteus to simulate with real hardware you don't have unique absolute real time. Prouteus simulation has own simultion real time wich depends on computer process power and simulation process load, e.g. proteus 1s is not uniform and equal to real time 1s so you have two asynshronous machines for communication one virtual and one real with different base times.
You need to experiment to find optimal combination of real and virtual baud rate. In some unmatched cases you can expect PC UART FIFO overflow or real hardware UART FIFO overflow.
I think that Proteus virtual COM port is excelent for testing asynchronous communications.
If your comunication protocol pass Proteus virtual simulation and real hardware communication it will always work with real hardware.
Regards