I checked and see that there is a current bug reported on this. I added a link to this discussion to that report.

I originally got the error when attempting to import an external file, and confirmed it by trying with the example file.

It's the release.

In[61]:= SystemInformation["Small"]

Out[61]= {"Kernel" -> {"SystemID" -> "MacOSX-x86-64", 
   "ReleaseID" -> "10.0.0.0 (5098698, 5098537)", 
   "CreationDate" -> 
    DateObject[{2014, 6, 29}, TimeObject[{20, 38, 32}]]}, 
 "FrontEnd" -> {"OperatingSystem" -> "MacOSX", 
   "ReleaseID" -> "10.0.0.0 (5098698, 2014062704)", 
   "CreationDate" -> 
    DateObject[{2014, 6, 27}, TimeObject[{23, 17, 40.}]]}}

It works fine for me Jesse...

In[2]:= SystemInformation["Small"]

Out[2]= {"Kernel" -> {"SystemID" -> "MacOSX-x86-64", 
   "ReleaseID" -> "10.0.0.0 (5098698, 5098537)", 
   "CreationDate" -> 
    DateObject[{2014, 6, 29}, TimeObject[{20, 38, 32}]]}, 
 "FrontEnd" -> {"OperatingSystem" -> "MacOSX", 
   "ReleaseID" -> "10.0.0.0 (5098698, 2014062704)", 
   "CreationDate" -> 
    DateObject[{2014, 6, 27}, TimeObject[{23, 17, 40.}]]}}



In[3]:= Import["ExampleData/temperatures.json"]

Out[3]= {"01/01/09" -> -6.06, "01/02/09" -> -2.83, 
 "01/03/09" -> -4.22, "01/04/09" -> 1.28, "01/05/09" -> -7.17, 
 "01/06/09" -> -4.83, "01/10/09" -> -2.33, "01/07/09" -> -2.5, 
 "01/11/09" -> -7.33, "01/08/09" -> -8.94, "01/12/09" -> -8.11, 
 "01/09/09" -> -6.78, "01/13/09" -> -8.17, "01/14/09" -> -14.11, 
 "01/15/09" -> -20.11, "01/16/09" -> -23.17, "01/17/09" -> -12.67, 
 "01/18/09" -> -9.22, "01/19/09" -> -9.67, "01/20/09" -> -8.67, 
 "01/21/09" -> -7.94, "01/22/09" -> -5.67, "01/23/09" -> -2.89, 
 "01/24/09" -> -11.78, "01/25/09" -> -15.61, "01/26/09" -> -12.89, 
 "01/27/09" -> -10.72, "01/28/09" -> -9.67, "01/29/09" -> -6.56, 
 "01/30/09" -> -10.61, "01/31/09" -> -7.61}