B_Mariner:
So I have more than one? Which does not surprise me, I am fairly new at this.
It's hard to know how you expect us to take things forward based on this reply.
In my opinion you have shown us far too much code and given us very little information. I'm lazy. I'm not going to take the trouble to study your code for 10 or 15 minutes to try to figure out what it does. But if you tell me I will certainly try to help.
What is a typical transmission from the PC to the Arduino?
How often is this data transmitted?
How is the Arduino supposed to respond to the data it receives?
...R