Leopard and Office don't mix together. Upon upgrading lost all my network printer drivers. Reinstalled them so they work from FireFox.
However Office crashes (quits) when I try to print. Same happens when I try to print to PDF, which worked great before upgrade.
Also Visual Basic macros in my Excel sheets crash Mac version Excel but work great under Windows Excel.
After 3 months of struggles I am sorry I switched from Dell to MacBook Pro.
It is fairly common for programs to fail when upgrading from one version of OS X to a new version.
But, frequently it goes much smoother if you backup all your data files, e-mails, bookmarks, address book, etc.
Then, do a fresh install on a freshly formatted hard drive.
Then, re-install your programs from scratch (using their original installation disks).
Then, copy your data files, e-mails, bookmarks, address book, etc. back to the system.
I find that things are much smoother that way.
Yes, an upgrade install would be nicer. But, since it tends to have more issues, I usually go the long way.
Fortunately, major releases of OS X only come along every few years. I use it as an opportunity to clean-up my system and dump the garbage I forgot about.