Ray, this is definitely interesting, but ultimately we need to figure out why the buffer overflow / Receive Error Flag causes the system to become unstable. Based on the seemingly random results I see when things go south, I am strongly suspecting that there’s a memory corruption problem. I’m wondering if the buffer overflow condition is allowing a memory overwrite to occur? Have you looked at the input buffer to see if it’s correctly declared? Does the code that writes bytes into the buffer check to see if the buffer has enough room for the current batch of bytes? If so, could there be a boundary condition error that’s causing a memory overwrite? I haven’t even attempted to look at the code in question, so I have no idea what it looks like, but based on my prior experience, I’m suspecting that a memory overwrite may be corrupting adjacent variables / code.