problem with image gallery

I am trying to upload an image to a site one of my clients built for them. Whenever I try to upload an image file to the page using the insert image button, I get this message:

The uploaded file could not be moved to /var/www/vhosts/emtec-engineers.com/httpdocs/wp-content/uploads/2011/04.

I am basically a print designer, although I am fairly conversant with html and css. But this has me stumped. Any suggestions would be appreciated.

Their web address is https://emtec-engineers.com/
The image is supposed to appear on the Project Experience page, title: Fourth Precinct