Multisite in a sub directory

Hello Everyone.

I know this is not the ideal situation, but want to know how I can make this work properly.

I am working on a site that is well established and was developed (partly by myself) using custom PHP and MySQL. The original developer was not a reduce, reuse coder so there are physical directories rather than using .htaccess to serve the subdirectories.

Anyways, my client wants a network of blogs based in the /blogs/ directory. The original site will be in the root directory of the site, while the WordPress install is located within /blogs/.

I was successful at installing Multisite and everything appeared to work at first glance. My main WordPress site was accessible at mydomain.com/blogs/ and mydomain.com/blogs/blog/. My 2nd WordPress site was accessible at mydomain.com/blogs/site2/.

All appeared to be fine…Until, I tried to create a post.

When I publish a post, or submit a form of any kind, the server sends me the file to download (post.php). I don’t want to download that. The changes are made to the database, but this funky file gets sent to my browser.

Additionally, the images that are uploaded to a post show up as a broken image, even though they are uploaded and show up when I view the post within the blog.

What should I be doing instead? Should I try using sub-domains instead? I need to leave the root of the site intact. I can’t alter that at all.

Any help is appreciated.