Error uploading images

Hi.

I was in the middle of trying to upload about 10 images. The first 2 uploaded fine then I got an error message which stated
Soccer marathon.jpg The uploaded file could not be moved to wp-content/uploads/2014/05.

Since then I cannot upload any images to any page. I’ve tried from a few different pc’s and the same message pops up.

The site is https://www.stfranciscollege-rochestown.ie and I’m running version 3.9.1 and the blogolife theme.

Any help much appreciated

Thanks, Denis