New User-Cannot Upload

Hey, I am new to Arduino and I am having issues uploading any programs. I have an Arduino Uno and I am running the 1.6.8 software on a Mac with OS 10.10. I have selected Arduino Uno under the board selection and /dec/cu.usbserial-DN00Q2DE as the port. The on light for the Arduino is on and a blue light by pin 13 is blinking. Whenever I try and upload any programs to the board this is the error I get.

processing.app.debug.RunnerException
at cc.arduino.packages.uploaders.SerialUploader.uploadUsingPreferences(SerialUploader.java:179)
at cc.arduino.UploaderUtils.upload(UploaderUtils.java:78)
at processing.app.Sketch.upload(Sketch.java:1178)
at processing.app.Sketch.exportApplet(Sketch.java:1152)
at processing.app.Sketch.exportApplet(Sketch.java:1124)
at processing.app.Editor$DefaultExportHandler.run(Editor.java:2417)
at java.lang.Thread.run(Thread.java:745)
Caused by: java.lang.NullPointerException
at java.lang.String.replace(String.java:2240)
at processing.app.helpers.StringReplacer.replaceFromMapping(StringReplacer.java:97)
at processing.app.helpers.StringReplacer.replaceFromMapping(StringReplacer.java:89)
at processing.app.helpers.StringReplacer.formatAndSplit(StringReplacer.java:37)
at cc.arduino.packages.uploaders.SerialUploader.uploadUsingPreferences(SerialUploader.java:174)
... 6 more

Any help would be appreciated.

1.6.8? Is that an hourly build? Those are likely to have problems - they should only be used by experienced users who are prepared to deal with bugs when encountered.

The latest released version is 1.6.7. Try using that, or better yet. 1.6.5-r5 which seems to be the most widely working of the 1.6.x versions.

Ah ok I just downloaded the 1.6.5-r5 and I am getting a compiling error.
avr-gcc: error: core.a: No such file or directory.

I got it to work!! I needed version 1.6.6. Thanks for the help.