With the black not printing, it could be a printhead fault. Even though it did appear to work when printing the screen shot of the same page, this can be due to the three colours mixing together to make the black, rather than the actual black ink being used.
One quick test is to print a text document from TextEdit. If this comes out blank then the black printhead/cartridge is faulty.
To check it, open Print & Scan and select the iP90v. Then click on Options & Supplies and select the Utility tab. Click on Open Printer Utility. With the Canon IJ Printer utility open, select Test Print from the drop menu and then Nozzle Check. This will output one sheet of A4 paper with the four separate colours. Does the black print? If no, change the drop menu to Cleaning and perform a Deep Clean. Then try the Nozzle test again. If the black still does not print then you will need to replace the black cartridge.
Thanks, PAHU. I pasted your answer into TextEdit, and it printed perfectly. As a further test, I printed your e-mail directly from the screen and it, too, printed o.k. I tried printing a Word document again and got the familiar blank piece of paper. (The iP90v makes all the usual sounds of the print head going back and forth and the paper emerges bit by bit, but no printing.)
It sounds like this must be a Microsoft problem, rather than an Apple or Canon problem. I'll persue that avenue.