I find it highly unlikely that it has anything at all to do with PBP (other than the obvious interruption to it). If so, I would think every user (having the exact same files loaded) would have the exact same issue - and, one would suppose, it would not be difficult to duplicate for the same reasons. I think that it must be some interaction with another process or service - perhaps a background application using the com port, USB access or internet connection- there are dozens of running programs active from the moment the power is turned on.

Has anyone disabled the files that start at power up? It is one of my pet peeves is manufacturers who seem to believe they own all of my computer's resources because I use one of their applications. I have found HP, Nvidia, and Adobe to be nearly criminal in their dis-care, but they are far from the only culprits. Starting with a minimal set-up and adding one line or application at a time may help to isolate what resource is causing the issue?