Few times I have found a small but annoying issue on Maximo when attaching Office 2007 files. Do you know those Excel, Word, PowerPoint files with xlsx, docx, pptx extensions? Yes, those!
If you are using Microsoft Internet Explorer it may happen that these files can be uploaded successfully into your DOCLINKS folder but when you try to retrieve them they are downloaded as zip files.
If you have this problem here is the solution for you.
Edit httpd.conf file of your IBM HTTP Server (look in the conf subdirectory) and add the following section at the end of it.
AddType application/vnd.ms-word.document.macroEnabled.12 .docm
AddType application/vnd.openxmlformats-officedocument.wordprocessingml.document docx
AddType application/vnd.openxmlformats-officedocument.wordprocessingml.template dotx
AddType application/vnd.ms-powerpoint.template.macroEnabled.12 potm
AddType application/vnd.openxmlformats-officedocument.presentationml.template potx
AddType application/vnd.ms-powerpoint.addin.macroEnabled.12 ppam
AddType application/vnd.ms-powerpoint.slideshow.macroEnabled.12 ppsm
AddType application/vnd.openxmlformats-officedocument.presentationml.slideshow ppsx
AddType application/vnd.ms-powerpoint.presentation.macroEnabled.12 pptm
AddType application/vnd.openxmlformats-officedocument.presentationml.presentation pptx
AddType application/vnd.ms-excel.addin.macroEnabled.12 xlam
AddType application/vnd.ms-excel.sheet.binary.macroEnabled.12 xlsb
AddType application/vnd.ms-excel.sheet.macroEnabled.12 xlsm
AddType application/vnd.openxmlformats-officedocument.spreadsheetml.sheet xlsx
AddType application/vnd.ms-excel.template.macroEnabled.12 xltm
AddType application/vnd.openxmlformats-officedocument.spreadsheetml.template xltx
Save the httpd.conf file and restart the HTTP Server.
Now you should be able to download those files without any problem.
Here is the original article where I have found the solution.
UPDATE! John spotted an IBM TechNote describing the official solution.