A lot of people didn't understand there could issues at the base level. They were exchanging files with their colleges on IT provisionned machines and didn't have to mind what they were using, on a day to day level they had no issues, it was the people "outside" that were a PITA always boyhering them.
Also biting the bullet and being on the latest version of Office with everything from Access to Outlook installed sadly covered all the bases. We worked on an intranet for a smallish company and they had web components that only worked with the specific Office DLLs installed. Took us an afternoon to figure out why it didn't work on our machines.