Brilliant. Changing to a different font worked. Now how do I go about replacing the faulty font (Arial, which is the default on all of our client's documents)? And what is MBP?
MBP is a shortening for MacBook Pro
Since you think it's one font, it won't take you long to replace the fonts:
1. On both computers, navigate to the Applications folder and open the application called "Font Book". This will open a sort of library of what fonts you have installed on your computer. Make sure you are viewing the "All Fonts" collection. Some fonts may have a yellow triangle next to them. You can ignore these for now, since we're concerned with Arial.
2. On the problem computer, right click on "Arial" and select "Remove "Arial" font family." Don't worry if you have other fonts with Arial in the name; this will only remove the one font and whatever fonts are in the collapsed list.
3. On the MBP, highlight "Arial" via left click. Then, go to File>Export Fonts... and follow the steps. Make sure to place the file on a spot you can easily find it again. This will produce a folder called "Exported Fonts" in your desired location. Inside this folder will be another folder called "Arial".
4. Using either a flash drive, a wireless link, or even e-mail, transfer the "Exported Fonts" folder from the MBP to the other computer.
5. On the problem computer, go to File>Add Fonts... and locate the "Exported Fonts" folder. Navigate to the Arial fonts and highlight them all (either using shift+arrow keys, or option+mouse clicks) and select Open. This will import the fonts to the "User" collection, but will function like it should.
6. Try opening the document from earlier to ensure the problem is resolved.
7. Close Font Book on both computers and you're all set.
Hope this helps.