Multiple file upload error

I have a page with four controls on it. When i upload less
than four meg across all four inputs, the files upload correctly. When i
upload more than four meg, i get an error message page the page cannot be
found. I have changed the . This does
not fix the problem. I can upload a single file > 4Meg, but not as a group.
Anyone have a similiar problem? What is the solution.