GPRS GSM + LCD Can They Work Together?

My project is reading sensors, displaying on 16x2 LCD and at intervals using the GPRS to send text messages. I can get the sensors to work and display. I can also get the text message to send, but when the LCD and the GPRS shield are both connected it does not work. There is a power flicker on LCD and the GPRS fails to connect to the network and needs manual reset. This also occurs when I disconnect power from LCD. I have no pin conflicts. GPRS shield rxTX are on pins 7/8. LCD are on pins 2-5 and 11/12. Only works when I disconnect the LCD pins 2-5. What causes the power flicker and is there a solution to have the LCD and shield to work at the same time?

Are you providing enough power?

What about any other pins used by the GPRS shield - Power or reset?