I have an Alesis Q49 MIDI keyboard. I have had it now for over a month, and whenever I use it with my laptop, it works just fine. However, when I plug it into my desktop and leave it plugged in over night, it doesn't work the next morning. I don't change any settings or anything. It works fine on my laptop over night, but not my desktop, so I know it's not the keyboard. None of the settings in my preferences change in Music Creator 6, but the program doesn't respond to any keys I press. It does, however, react to any buttons I press on the keyboard (such as octave changes)
 
Does anyone know why it stops working after being plugged in for so long?

I for one, would not leave my DAW computer running overnight. I shut it off when I am finished working on music and also shut down everything associated with the studio..... including keyboards, interface, monitors, speakers, etc.....
 
I don't want to risk a surge coming in on the electrical lines and frying my gear. Thunderstorm, car accidents hitting poles etc....
 
As to why one keeps the connection and the other loses the connection.....?  Perhaps it's related to the power, standby,  and sleep settings in the machines.
 
There has long been a debate on whether it's better to leave a computer on or shut it down when not being used..... I prefer to shut it down. Shutting it down also clears the memory locations from all the stuff it tends to accumulate from running. I service computer based security systems and the first question I ask on a service call is.... when was the last time you shut this system down and did a cold boot? It's amazing how often that simple step puts the system back to running.