Advanced Help Needed

I need some help figuring something out that my host denies is his problem. I have a suspicion that only someone who has run into this problem once before has the answer. I have this form which posts to a PHP file. Sometimes I pass a file along. This was info for a database and a picture along with it. This worked fine for the longest time. Now it does not. when I post a file in the form I recieve an "Cannot Find Server". When there isnt a file posted then the form works fine. I dont understand because I recieve no PHP generated error messages, but rather a problem finding the site entirely. Has anyone ever seen this? Help would be much Marc Davenport