The MCU sends data continously.
You could verify this with hyperterminal.
Your VB.NET may have timed-out between ROOM and ACTIVATED characters.
Or the RX buffer on the PC is low.
What you could do is just send small data from the MCU and decode it in your PC program.
For example, the MCU just sends "RA\n" and it will be interpreted and printed as "ROOM ACTIVATED" by your VB.NET
This way, hindi siya putol dahil maliit lang ang sent charactes.