Re: Kirby Dream Land 3 and others.. controller problem.
It's not actually a problem with your gamepad. It's a problem with the emulated SNES.
Remember, the game doesn't know what your PC controller is.
It only knows what ZSNES says is there, which is usually a standard SNES gamepad or 3.
A real SNES would throw up exactly the same error if you had something other than a gamepad connected to either controller port. As I understand things, it has to do with the power draw of the coprocessor+accessories exceeding the AC adapter's rated maximum wattage.
Your virtual SNES has something connected to one of the virtual controller ports, and the virtual cartridge is stopping so it doesn't blow out your virtual power supply.
That makes more sense than it sounds.
The graphical controller window MEKA shows makes this concept a lot easier to explain.
Anyways, now that you know the problem, on to the solution!
"Disconnect" controllers 3-5. Open the controller config menu, highlight NONE, then click SET.
Alternatively, set 5 to NONE and check "USE PL3/4 AS PL1/2" to "disconnect" controllers 3 and 4 without totally unmapping them.
This will disable multitap emulation, which is automatically enabled when you have more than two controllers "connected."
And in the Devices window Agozer mentioned... make sure BOTH controller ports are set to gamepad.
This will disable mouse/lightgun emulation, if it's been enabled somehow.
Now reset the game. If all goes well, it will boot just fine.