Produxtor

I've been using Missing Sync to sync Excel and Word docs on my Tilt since I switched from a PC to Mac environment. Everything is fine until I try to open an Excel document on my Tilt that has been saved on my Mac Book with MS Excel for Mac 2008. One of the sites that I visited (don't remember which) suggested that I needed to upgrade to Windows Mobile 6.1 so I downloaded it. However, when I tried to install it the message I got said that my version of Mobile was newer than the one I was trying to install - so I didn't. Any suggestions on how to get Excel Mobile to open a file written with Excel Mac 2008? Incidentally, Word documents open just fine.