Thanks Clootie. I made a demo for you, and I get exactly the same errors (source included):

http://www.teleportmedia.com/mundano/Mouse.zip

This is the output I get:

Code:
Creating DirectInput, result = 0
Creating system mouse device, result = 0
Setting data format, result = 0
Setting cooperative level, result = 0
Aquiring device, result = -2147024891
Getting device state, result = -2147024884
Aquiring device, result = 0
Getting device state, result = -2147024809
Aquiring device, result = 1
Getting device state, result = -2147024809
Aquiring device, result = 1
Getting device state, result = -2147024809
Aquiring device, result = 1
Everything goes fine in the initialization, then I can't read nor acquire the device. It's weird. :?