xlsx attachment can not open on a smart phone

[ArtimusPrime]

I can create an xlsx file using excel 2007 on my computer. Send it to my smartphone, and open it.

I then have our cognos server send me and xlsx report and I get the following:

An error occurred reading "[Report Name]” because the file format is not recognized.”

I hope some one can help me with this I'm stumped!! This is going on with everyone's phone in our organization. Our phones are all running Windows Mobile 6.1 also.

I'm stumped