image upload error message

I am trying to upload an image file to an item in Omeka 1.5.1 I've done this in the past, but this time every time I hit save I get an error message and the image won't upload. It just provides a link with directions on how to reveal the error. I find these directions completely unintelligible and am a bit stuck. Suggestions?

To move forward you really do need to follow those instructions about revealing the error.

For Omeka 1.5, the process is just editing one line in two files.

Ok but what does this mean ".htaccess file in the root of your Omeka installation"? I did a search for ".htaccess" and for "omeka" and didn't find anything on my harddrive. I had a student (who is no longer at GMU) set up the website, I am just making updates. Does Omeka need to be installed on my laptop to upload images? I have been making text changes without a problem and in the past I added images as well, so I'm not sure what is going wrong now.

Are you still using the version hosted at CHNM?

You will need access to the web server, for example via an FTP application, or in shared hosting CPanel, and a username and password for accessing the server. From there, you'll need to know where Omeka is installed. That's the root of the Omeka installation. You'll also want to make sure that your FTP program (or whatever way you access the server), will show hidden files.

Omeka does not need to be on your laptop -- the key starting point is access to wherever it is on your server space.

Yes, I'm using the version hosted at CHNM.