I’m working on a Christmas / Holiday light display for my house. I’m using ws2801 based leds and I’m having issues getting them to work when wired up on the house. There are 133 pixels and I’m running 12v power injecting to every other strip. My data/clock run is about 20 feet on 16 gauge speaker wire. I’m not using hardware SPI because that is being used by the ethernet board that will receive user input. It only worked once and had glitches where the wrong color would display on a pixel. Now only about the fist 20 or so pixels light up and they are random colors or flashing as if the data/clock isn’t connected. Is my run length an issue or should I go back and resolder all my connections?
I found that for long runs I needed to use twisted pair. Plus, make sure that the ground on the leds is shared with the arduino’s ground (in addition to the power supplies for the leds), I found that to be especially important with long runs (I use cat5 ethernet cable, and put clock/ground on one twisted pair and data/ground on another twisted pair, then tie the grounds together with the power ground at the leds).
Also, it is possible that the software SPI is running too fast (WS2801’s clock out at 1Mhz, the data-rate mapping for software SPI is a bit off the cuff at the moment, so you may need to adjust the clock speed, e.g.
LEDS.addLeds<WS2801, 13, 14, RGB, DATA_RATE_KHZ(800)>(leds, NUM_LEDS);
or
LEDS.addLeds<WS2801, 13, 14, RGB, DATA_RATE_KHZ(1200)>(leds, NUM_LEDS);
to try shuffling the numbers around a bit.
Finally, make sure that you’ve upgraded to RC4 - there were a couple of arduino glitches w/the software SPI that snuck in.
Thank you for the detailed reply. That gives me a lot of things to try when I get the time. 
I’m still learning alot about low voltage electronics etc., if I have several strips like these http://www.amazon.com/string-waterproof-module-WS2801-Digital/dp/B00DIBUDIC/ref=sr_1_1?ie=UTF8&qid=1382990620&sr=8-1&keywords=ws2801+led+pixel can I apply 12 volts on both ends of a strip or am I creating a short that will burn things up?
You can apply power to both ends
I’m doing a clone of my first setup and cat5 worked the first go round so I’m doing it again. Now my issues are that the first pixel blinks (low power on all 3 colors) and near the end of my 187 pixel run I have a short gap (about 2 feet) and after that gap the pixels go crazy, obviously getting bad signal. I’m planning to switch out the wire I’m using (at the gap near the end) and go with cat5 for the signal but I’m having more issues with random errors throughout the run. I’ll play with the clock settings and see if that changes anything. Are there any other ideas to clean up or boost the signal?