Tim:
If you have the liberation fonts installed, they do a good job of replacing the usual Windows-expected fonts, and freely. Your computer's much more likely to substitute a good choice of font, rather than a bad one, when you don't have the Windows font that the author wanted to use.
Alex:
I do have the liberation fonts installed:
In this case, I don't think they'd help, because I don't think they have a replacement for Verdana.
Find us a few more problem pages, and we'll see if the cause is down to the same issues, or something else.