Since you answered "No Issues" to question #2 - it seems to me to be your application & what PB / O/S features you are using in combination with PB 12.6. Very and weird and frustrating when it works in previous versions of PB! 
Just for fun ... can you try running a few instances with the DEBUG option turned on?
ie: Application.exe /pbdebug
(your application will be slower though in this mode)
a) maybe that might tell us something when it hangs
b) slowing the processing down is another thing if it works.
Just a thought ... it might also be related your DB Client software that the PBVM calls when you issue a DB Connect in your application.
Q: Any Touch Screen services running?