SurferTim:
All SPI device libraries I deal with manage their own slave selects once the SPI devices are started. The low level library functions pull the slave select LOW, do the read/write, and set it HIGH again when finished. There is no need for you to do that in your code.The only no-no I know of is do not read or write to a SPI device during an interrupt. (edit: Meaning not in the ISR function itself.)
the Display has a interrupt pin at Pin 2, which is connected to a shield. I have to read a bit more about it. Does most libraries handle interupts ? Does arduinos Wifi library do interupts for buffering or something? It might be very likely due to it has to monitor for packets? There must be a wait function till an interupt is free if im not mistaken.
CrossRoads:
However i was confused if there was a need to connect a cable to 53. As is already has a connection to the WiFi shield by the ICSP Header I assume it handles it already, since it worked previously with all devices.
There is no SS on the ICSP header tho - Only SCK/MOSI/MISO and Reset/Pwr/Gnd.
So if you're going to use 53 and the shield does not plug in the Mega dual-row header, then and jumper is needed to where SS is on the shield.
So in this case, since WiFi SS is pin 10, I would have to do a jumper between 10 and 53? As its a shield for Uno and up, it doesnt connect to 53 in any way at the moment.