Thanks for the replies but I've found out that the problem was due to the stickduino. I switched to an ardunino nano v3 and everything is working perfectly but now I have another problem.
The LCD works great and so the SD card reader. But when I try to use them at the same time the LCD becomes extremely slow. 
Pleae take a look at this sample of code:
#define cs_lcd 10
#define cs_sd 7
#define dc 9
#define rst 8
#include <Adafruit_GFX.h> // Core graphics library
#include <Adafruit_ST7735.h> // Hardware-specific library
#include <SPI.h>
#include <SD.h>
Adafruit_ST7735 tft = Adafruit_ST7735(cs_lcd, dc, rst);
File myFile;
void setup()
{
tft.initR(INITR_REDTAB);
tft.fillScreen(ST7735_BLACK);
tft.setTextWrap(false);
}
void loop()
{
tft.setTextSize(5);
tft.setTextColor(ST7735_RED, ST7735_BLACK);
for ( int i = 0; i < 100; i++ )
{
tft.setCursor(40, 50);
tft.print( i );
delay( 100 );
}
}
This sample of code works perfectly without any problem. But if I add a simple function to open and write data to a file it will start lagging severely:
#define cs_lcd 10
#define cs_sd 7
#define dc 9
#define rst 8
#include <Adafruit_GFX.h> // Core graphics library
#include <Adafruit_ST7735.h> // Hardware-specific library
#include <SPI.h>
#include <SD.h>
Adafruit_ST7735 tft = Adafruit_ST7735(cs_lcd, dc, rst);
File myFile;
void setup()
{
tft.initR(INITR_REDTAB);
tft.fillScreen(ST7735_BLACK);
tft.setTextWrap(false);
}
void loop()
{
tft.setTextSize(5);
tft.setTextColor(ST7735_RED, ST7735_BLACK);
for ( int i = 0; i < 100; i++ )
{
tft.setCursor(40, 50);
tft.print( i );
delay( 100 );
}
writeCard();
}
void writeCard()
{
if (!SD.begin(cs_sd)) {
//Error accessing SD CARD.
return;
}
myFile = SD.open("tmp.txt", FILE_WRITE);
if (myFile) {
//WRITING TO FILE
myFile.println("Lorem ipsum dolor sit amet, consectetur adipisicing elit, sed do eiusmod tempor incididunt ut labore et dolore magna aliqua.");
// close the file:
myFile.close();
}
}
I though that this could have something to do with the SS, after all I'm enabling the SD pin without disabling the LCD one but still no good. 
void writeCard()
{
//TRY TO DISABLE THE LCD SS PIN
digitalWrite( cs_lcd, HIGH );
if (!SD.begin(cs_sd)) {
//Error accessing SD CARD. Re-enable LCD SS pin, force the SD SS pin to be disabled and exit.
digitalWrite( cs_lcd, LOW );
digitalWrite( cs_sd, HIGH );
return;
}
myFile = SD.open("tmp.txt", FILE_WRITE);
if (myFile) {
//WRITING TO FILE
myFile.println("Lorem ipsum dolor sit amet, consectetur adipisicing elit, sed do eiusmod tempor incididunt ut labore et dolore magna aliqua.");
// close the file:
myFile.close();
}
//Writing finished. Lets re-enable LCD SS pin and disable the SD SS pin.
digitalWrite( cs_lcd, LOW );
digitalWrite( cs_sd, HIGH );
}
I would really love not to have to hack (aka mess with) the Sd.h but right now I feel like I've hit a wall.
Any ideas?