can’t upload or access images

I’m having such a hard time uploading images into a post. I’ve tried several times and changed all the permissions on the wp-content directory and everything inside it to 777. When I try to upload images into a post or a page, I get an HTTP ERROR. I can’t find information or documentation for this anywhere. I’m using Firefox but have tried in IE v. 7, with the same error message.

I looked on the server through my FTP client and found an “uploads” directory was created in the wp-content folder and even tried uploading the images myself via FTP, but I can’t access a thing. Is this a common problem? I can’t find anything to help me fix it. I’m not a Bill Gates, but this seems pretty basic and I just can’t figure out what to do.

Thanks in advance.