It may also be worth mentioning that although this problem (Dolphin crashing when trying to configure a second joypad in the Wii Remote Plugin configuration) also occurs in older revs of Dolphin (eg R3286) in those builds I can use both controllers in game without any problems. Copying plugins from older versions didn't work, as did trying the nJoy plugin.
MB: Asrock 4Core1600Twins-P35D
CPU: Intel Core2 Duo E8400 @ 3.0 GHz
GPU: XFX GeForce 9800GTX+
RAM: 2 GB DDR3
OS: MS Windows Vista Business SP2
CPU: Intel Core2 Duo E8400 @ 3.0 GHz
GPU: XFX GeForce 9800GTX+
RAM: 2 GB DDR3
OS: MS Windows Vista Business SP2
