You haven't provided a link to any information about the shield so I don't know which pins it uses but there is a good chance that if it's software uses interrupts then there is also a good chance that it uses digital pin 2 and/or 3. In that case it's software can affect your LCD even without the shield being connected.
Like I mentioned in intinial post, I do not even plug in the shield and then upload to UNO r3 and the display wll become corrupt after the initial wait has ended.
The shield is a HANRUN
HR911105A Ethernet shield widely used for Arduino
* LCD RS pin to digital pin 12 //8 on UNO
* LCD Enable pin to digital pin 10 //9 on UNO
* LCD D4 pin to digital pin 5 //4 on UNO
* LCD D5 pin to digital pin 4 //5 on UNO
* LCD D6 pin to digital pin 3 //6 on UNO
* LCD D7 pin to digital pin 2 //7 On UNO
* LCD R/W pin to ground pin 5 on display
LiquidCrystal lcd(12, 10, 5, 4, 3, 2 );
The specific pins used by the interrupts are a function of the microprocessor chip and cannot be changed, but the LCD (assuming it is not also on a shield) can use any available I/O pins.
Also - go back and edit your original post, highlight the part that is code and click the 'code' button - it looks like a # symbol. It should then look like the code that I have quoted above.