Is it only onscreen or on the form printout?
What's happening is the Wingdings font that is used for the checkboxes is getting replaced by another font, and the corresponding character in that font is actually a lower-case letter q (which looks like a backward p).
If it's only happening on the printout, you go into Configure>Preferences>Print Options and check "Force print true type as graphics" and click Ok. That will avoid the font selection altogether when printing the form.
If it's happening onscreen, it means you have some alternate version of Wingdings installed. If you didn’t have a version of Wingdings installed, the program would give you an error message on opening that you need that font. But if you have Wingdings 2 installed, the program would probably just launch, even though Wingdings 2 isn't going to cut it. You can either download the Wingdings font online or email CEB technical support (email@example.com) and we can send you the fonts to copy/paste into your, (under Start>Computer) C:\Windows\Fonts folder, and reboot the computer.
Then, see if you still have the strange character in place of the check boxes.