OS X :: Unable To Attach Numbers And Pages Documents To Emails?

I've done some work on Numbers and Pages (both 2008) on my MacBook. For some reason when I try to attach these documents to an email to send to my boss, they are grayed out so that I cannot click them and attach them. I've tried using my university's system as well as hotmail, ymail and gmail, so I assume it has something to do with recognition of the files. So far, I have tried to change the Numbers documents to .xls, but this does not solve my problem.

In this form, the properties ("Get Info") tell me that it is a Microsoft Excel document, but Numbers won't open it and in won't send via email. I have other .xls documents on my computer that I either received by email or downloaded, the icon on my desktop is different, Numbers reads it and they can be attached to emails. It seems that even though I change the .numbers files to .xls, there is still something missing for them to really be Excel files or at least sendable.