Python2.7 Active Console to Prevent Deadlock?

Question

I noticed an interesting behavior for my system on Windows XP

To debug my system, I used cmd console to start the server

xProcess = subprocess.Popen(args='Python.exe ClntMgrSvrFact.py', creationflags=CreationFlags|win32con.CREATE_NEW_CONSOLE)

For each client(MSExcel) connected via TCP/IP, server factory will spawn a new process using

xExeMgr = subprocess.Popen( 'Python.exe ClntMgrSvr.py', stdin = PIPE)

In this way, xExeMgr will have its output to the xProcess console (name as xPConsole).

For testing purpose, I put both my client and my server in my local.

Then the interesting part, if I switch to any other window/console on my desktop, the xExeMgr will go into deadlock.

If I switch to xPConsole on my desktop (put it to the front), xExeMgr will proceed just fine. Can anyone give me an explanation?

What's the meaning for activate/switch to a particular window/console in XP? Higher priority?