As explained at french XOOPS support
( http://www.frxoops.org/modules/newbb/viewtopic.php?topic_id=1070&start=0#forumpost5809), we encounter
some mistakes with MS Office files (xls, ppt).
Files are uploaded without any errors, stored in the
correct directory, but are not displayed in posts...
Don't know why ?

I tested without any success
- to switch to another browser (IE vs mozilla)
- to work in prod environment to prevent O/S platform
errors (win easyphp vs unix)
- to use usual file names (without trailing blanks or
special caracters)

Please help ...
marco

nb I upgraded from newbbpro to newbb2
nb2 I've just submitted at dev.xoops.org