This problem might be of Motherboard, But you need to first check other situations like issue with USB port, SMPS, Drivers etc......I had the same problem where my mouse and keyboard which were connected to USB ports rather than PS2 port use to disconnect frequently for 6-7 seconds and then reconnect.(for over 4 months) and i lost all hope. In my case power was coming from Power socket to UPS, which was further supplying to SMPS. I read all similar forums and utilized every trick which i can deploy like changing power settings, disabling gestures, updating drivers, changing OS, new mouse/keyboard etc...
Finally i changed SMPS, it did gave some hope for 1-2 days, But still issue not resolved. Suddenly an idea came to my mind of placing VOLTAGE STABILIZER to this whole unit....What i did: Placed Voltage Stabilizer in between UPS and Power socket. and of my surprise Issue got resolved. And it's been 2 months i haven't faced that issue and really happy to share the solution which could be applied by many users.