The Win7 has implemented a new font system. I dont totally understand it yet, but problems like this can occur when a font is replaced, or is just working in place of the provided font items.
Here is the only explaination I can do so far: The new fonts can have layers of typefaces in them, notice how Large thier file sizes are. These layers can have multiple fonts and bold and ital and even other fonts and languages in them. The previous font were simple small and uncomplicated. If one of these fonts this web header is using (view the web source code) Was replaced or just hanging out there being used, instead of the system finding the type it was thinking was there, it would show what is in this replacement font item.
Get into your fonts folder (preferably with something that actually shows "details", but getting in with winders might show you) And compare the 2 font folder structures between the machines. and delete away :-) . the system protects the primary system fonts, sooo you cant do to much damage :-) but having a backup before deleting stuff comes in handy .
Then it wouldnt hurt to clear the font cache, after you find that weird font that dont belong, or even do that First to try and fix it by just clearing the font cache thing.
Alternativly and for testing, you could use whatever resources they provide in the program to ignore the websites fonts, and force your own font in.
side notes: Fonts can also be set by the web pages CSS style sheet, so if you cant find the offending item in the webs "source code" then you can find it in the style sheet that came in with the web site. The purpose of knowing the web source font used, would be to know which font it likely is that has been replaced or is overriding.