Yes, I was having the same problem, and the exact same happened for me my keyboard and mouse Just kept cutting out, However I Fixed it by Learning that It Just doesn't have enough power to keep supplying the keyboard and mouse with power plus if you have Ethernet Connection (Internet Wire) Which I didn't actually have the demand for power is High for the poor thing and the result is it cant cope so gives up eventually and shuts down components such as the Keyboard and mouse and maybe your Ethernet Port to free up power for other Raspberry Pi components such as the CPU, GUI and RAM, The HDMI Output etc. This Isn't a Error or fault It Just means you need to check you have the correct Power supply Hooked up to the Raspberry Pi, It needs to be 2.5 W (model A) and 3.5 W (model B) But If you still have Problems or you do defiantly have that, what I ended up doing (Because I don't have any Power leads of 3.5 W!) Is connecting a USB Hub via one of the USB Ports (One Like this will do, http://www.amazon.co.uk/BargainUniverse ... 960&sr=8-3
) and as-well as Powering the Raspberry Pi, Power the USB Hub to Via the Input In (It's Normally a round type of 5V Input on it somewere, But some do not have it) and plug the Keyboard and mouse into the USB Hub so the USB Hub powers the Keyboard and mouse or In some peoples case Just a Keyboard and there you go! Sorry About the Long Answer really Hope this helps!
The Idea is to free up power so you can power more complex stuff! Or you could buy a Very Simple boring low powered Keyboard and Mouse!