Maniac, I think you may have a bug in your pin mappings.
In variants\avr-developers\pins_arduino.h, the comments indicate the analog pins for the Sanguino are mapped like so:
// ATMEL ATMEGA644P / SANGUINO (also works for ATmega1284P)
//
// +---\/---+
// INT0 (D 0) PB0 1| |40 PA0 (AI 0 / D31)
// INT1 (D 1) PB1 2| |39 PA1 (AI 1 / D30)
// INT2 (D 2) PB2 3| |38 PA2 (AI 2 / D29)
// PWM (D 3) PB3 4| |37 PA3 (AI 3 / D28)
// PWM (D 4) PB4 5| |36 PA4 (AI 4 / D27)
// MOSI (D 5) PB5 6| |35 PA5 (AI 5 / D26)
// MISO (D 6) PB6 7| |34 PA6 (AI 6 / D25)
// SCK (D 7) PB7 8| |33 PA7 (AI 7 / D24)
// RST 9| |32 AREF
// VCC 10| |31 GND
// GND 11| |30 AVCC
// XTAL2 12| |29 PC7 (D 23)
// XTAL1 13| |28 PC6 (D 22)
// RX0 (D 8) PD0 14| |27 PC5 (D 21) TDI
// TX0 (D 9) PD1 15| |26 PC4 (D 20) TDO
// RX1 (D 10) PD2 16| |25 PC3 (D 19) TMS
// TX1 (D 11) PD3 17| |24 PC2 (D 18) TCK
// PWM (D 12) PD4 18| |23 PC1 (D 17) SDA
// PWM (D 13) PD5 19| |22 PC0 (D 16) SCL
// PWM (D 14) PD6 20| |21 PD7 (D 15) PWM
// +--------+
And as near as I can tell, this is correct. However, where the pin constants are actually defined below you have:
static const uint8_t A0 = 24;
static const uint8_t A1 = 25;
static const uint8_t A2 = 26;
static const uint8_t A3 = 27;
static const uint8_t A4 = 28;
static const uint8_t A5 = 29;
static const uint8_t A6 = 30;
static const uint8_t A7 = 31;
I'm not sure where those constants get used, but they're opposite what the comments seem to indicate they should be.