The rectangles are in place of a letter as your computer cannot 'find' the font! I get it at work a lot as I use heaps of different fonts, a lot I've downloaded and sometimes I even have to send the printer font files as they can't find some of the weird and wacky fonts I use! Usually your computer will try to substitute the font it is 'seeing' with something similar, if it doesn't find anything, you'll just get a rectangle - don't ask me why a rectangle, I have no idea! Hope this helps!
WP Math B should be a set of mathematical symbols, like parenthesis, 'parts' of boxes etc . . . the others I've never heard of and I don't have WP on this PC so I can't look!
