When I move from my desk to my couch, I unplug my laptop and the external monitor. 90% of the time it will freeze within 1 minute. First, the sound will stutter like this, go normal again, but the screen is frozen, and around 10 seconds after that I get a BSOD with DPC_Watchdog_Violation.
Other things to note: I have no unusual programs running (most of the time just Chrome or Winamp, if at all.) Sometimes I have an external HDD connected but I'm 90% it happens without it too.
When you disconnect from the external monitor you should really turn off the laptop first. It is quite easy for a laptop to react badly when removing external items (like a monitor) without turning off the laptop.
And if you are in the middle of watching something or playing something that has video and sound, if you don't stop or pause in when making the change (if you don't turn off the laptop) then having the item stop, freeze, stutter, even need to be restarted is very normal.
Start by pausing whatever you are doing before removing the external monitor and see if that resolves it. If it doesn't, then be sure you shut the laptop down when you make the transition.