Downloading some file type

the webexplorer was working well, but not any more, 
i can upload file (any type), but i can not download microsoft file such as word (.doc) although the file size is less than 200kb.
recently, i installed openxml sdk ver.2 on the server, i thought this is the reason, i uninstalled it but the same problem.
please note that i can download .txt, .jpg, .ods, .odt,