First of all, thank you very much for taking the time to write, I really do appreciate it! :^)

I can most certainly relate to the symptoms you describe although in my case, they never lasted more than a few seconds at a time.

The first thing to do would be to ensure that you are using the latest version of your Bluetooth software and firmware — both are equally important. Should you not use the internal module, ensure that you are using the approved D-Link one and not another brand, which may work but which will lack some specific functionalities that have been designed to avoid the behavior you describe.

Finally, pay attention to potential sources of interference around you such as other bluetooth devices, AirPort base stations (or just about any wireless router), cell and cordless phones or metal paneling. Your keyboard and mouse have all been designed to work in challenging environments but it can happen that, for some reason that remains to be discovered, there are extremely heavy interferences around your Mac.

You might also want to test your keyboard and mouse in another location on another computer — if necessary, ask an Apple Store to lend you an iMac for a couple minutes — in order to ensure that your devices are not damaged in any way.

Let me know if this helps!

FJ