SPI woes

I've been going through hell using SPI to communicate with a digital potentiometer.

Check this out:
I send this to Espruino:

SPI2.setup({scl:B13,miso:B14,mosi:B15});

digitalWrite(C4,1);

var digipot=require("MCP4xxxSPI").connect(SPI2,C4,1,128);

so digipot.getVal(0) should return 319 (actual value is 63, but it's adding 256 to it due to a bug in my module code - not accounting for differences between parts). Look what happens!

 _____                 _
|   __|___ ___ ___ _ _|_|___ ___
|   __|_ -| . |  _| | | |   | . |
|_____|___|  _|_| |___|_|_|_|___|
          |_| http://espruino.com
 1v69 Copyright 2014 G.Williams
>echo(0);
=undefined
>digipot.getVal(0);
=0
>fs.readdir("");
=[
      "BlackBerry",
      ".Trash-1000",
      "dash"
    ]
>digipot.getVal(0);
=319 
> 

I have had it in failing state for hours, then one file system access, and bam, it's fixed.

Module code is here:
https://github.com/SpenceKonde/EspruinoDocs/blob/master/devices/MCP4xxxSPI.js