problems seeing files

I'm working on what so far is a very simple script. I've uploaded a file to a directory on a web host (two of 'em, in fact) and have this little script that's just trying to open the file and read it (for now). The script is not in the upload directory. All directories and files have at least 644 permissions. I can go in with FTP and Telnet and access both the script and the file in question, but when I run the script from my browser, it cannot see the file! One host says I don't have permissions to access the directory containing the file, the other just inexplicably says the pathname doesn't exist. (The former host forces SETGID flags on all scripts for some reason.) This seems totally weird to me. Has anybody run into this problem before? Thanks -David Schwartz