problems with GLCD


Hi guys, i have a GLCD 128x64 connected via SPI with Arduino Mega 2560, also i have a SD module connected via SPI.
When SD have comunication with arduino MISO or MOSI the glcd shows two horizontal lines on the picture I have on screen at the time, gives the appearance that distorts the image when communication with the SD, how I do to prevent that from happening?, thanks