Printers disappeared; network crawling

I'm having two problems on one machine, while several other Macs on the same network are not experiencing either issue.

First, my MacBook Pro can't find either of the two Bonjour printers on the network. In fact, I printed a PDF to one of these printers, and the moment that that document finished printing, I tried to print a second PDF; suddenly the computer was saying the printer was offline. I rebooted the MBP and restarted the printer hardware. I tried to delete and re-add the printer to my Printer pref-pane, but the computer could find no printer on the network. Meanwhile, I was able to print from an iMac with no problem whatsoever.

Second, the network connection on my MBP has slowed to a crawl. It took this Apple Support page about 20 seconds to download. Again, the iMac has no such problems; websites are snappy.

I am totally blumfustered. Absolutely no clue as to what could be the issue. It's not like I made any changes to the computer in the few seconds between printing the first document and trying to print the next one. Frankly, I wasn't sure whether to put this question under hardware or software, under printing or networking, because I don't have a clue as to what is failing or where. Anybody have any ideas?