spreadsheets are opened read only

Hi guys. I am having a problem with opening xls files from a link generated from php script. Let me analyze this: I have two linux servers with apache (php,mysql etc) that are running the same project. There is a part in this project that reads all the files from a directory and generates the appropriate links to them. These files are usually spreadsheets (xls) and when I open a file using the link on the first machine it opens normally but when I open the file from the second it is opened read only. I have checked the rights and the ownership and they are the exact same from the servers document root to the file itself. Any ideas why is this happening? -- Thodoris