I've never used the LCD library that you're using, but I have been working with the Ds1307 code for the last couple of days.
Try casting the bytes to int before printing them:
Serial.print(int(minute), DEC);
Serial.print(":");
I didn't get compile errors from this, but I did find that Serial.print() would print unreadable characters without the cast to int...
Might help.
Tim