Flickr Image Loader Error

Hi, I am using the ImageLoader library (which can be accessed at https://github.com/keshrath/ImageLoader) to access images from Flickr into Processing. A few days ago, everything was fine, but suddenly the sample code returns an error almost evertime I attempt to run it. The error reads

"org.scribe.exceptions.OAuthConnectionException: There was a problem while creating a connection to the remote service."

and then goes on to say,

"Caused by: javax.net.ssl.SSLHandshakeException: sun.security.validator.ValidatorException: PKIX path building failed: sun.security.provider.certpath.SunCertPathBuilderException:unable to find valid certification path to requested target "

Here is the sample code I am trying to run: so far I've tried replacing my API Key, using a different computer, and using different websites to load images from (google and tumblr), but so far nothing has worked.

import at.mukprojects.imageloader.*;
import at.mukprojects.imageloader.flickr.*;
import at.mukprojects.imageloader.image.*;

String apiKey = "yourApiKey";
String apiSecret = "yourApiSecret";

ImageLoader loader;
ImageList list;
Image img;

void setup() {
  size(800, 450);

  loader = new FlickrLoader(this, apiKey, apiSecret);
  list = loader.start("sunset beach", false, 60 * 1000);
}

void draw() {
  if (img == null) {
    img = list.getRandom();
  } else {
    image(img.getImg(), 0, 0, width, height);
  }
}

void mousePressed() {
  img = list.getRandom();
}

Any help with diagnosing the issue would be really great, thanks!