LiquidCrystal_I2C lcd(0x27, 2, 1, 0, 4, 5, 6, 7, 3, POSITIVE);
Are you sure that the pins called out in the constructor are correct? There is a LCD guesser program to help find the correct pinout for different LCDs. I'll try to find it.
edit:
[SOLVED] Using I2C 16x2 LCD with Arduino - Displays - Arduino Forum You can find to download the guesser form this post.