Pin13 causing Arduino uno to Freeze

Hello All. This is long winded but bear with me. I built 2 projects recently. The first project was an Arduino Uno with an ethernet shield that acts as a web server and the Sainsmart 8 relay board. It listens in the Viod Loop for incoming http requests and triggers different relays depending on a string in the request. if i send$1 it sets output pin 3 low and closes the relay. If I send it$2 it sets output pin 3 High and opens the relay. I repeat that for 7 of the 8 relays and it works perfectly. I use pins 3 4 5 6 7 8 9 as output pins. Then in my next project I bought a ir led emitter/ detector pair from adafruit and ran some code that captures ir remote's code and prints it to the serial monitor. Then I took that data from the serial monitor to and put it in a sketch to flash an ir led to control a device. That also works perfectly

Here's where it gets tricky. I tried to merge the 2 projects so that I could flash the led on pin 13 if the Ethernet shield receives a specific string. as soon as I put the led on pin 13 the Ethernet server stops responding. when I pull the wire off pin 13 the web server resumes. I didn't include the code here but thought someone might have an idea before I pasted a ton of code. If you need to see it I certainly can. Thanks so Much!!

Pin 13 is the SPI SCK pin. If the Ethernet board uses that, this is probably the reason.

Thank You!! That must have been it. I used pin 3 instead and it worked like a charm. It never occurred to me that the ethernet shield would be using some of those pins. I overlooked the obvious.
Have a Great evening!!