My impression is that this is recent problem with Snow Leopard, its version of Quicktime or Safari. I am positive that I read patents using Safari 4.x on Snow Leopard until some time in December. I was busy with the holidays, so it wasn't until late in December that I noticed the functionality had disappeared. I can still read the Tiffs using my old Powerbook G4 running OS 10.4.11, where both Safari and Firefox can view patents at the USPTO website. It's hard to believe that Apple cannot fix this. AccelView Tiff figured out the USPTO made some change on December 9, 2009 that messed up its plug-in. Maybe that change is to blame.
The Accel ViewTiff Plug-In works better than nothing on Firefox, but not well enough for my $59. I'd like the window to be adjustable so that I can enlarge the images at will and view them without having to scroll in that itty bitty little window.
If you already have the patent number, sometimes you can use google.com/patents. Unfortunately, Google's indexing is full of errors, and the more recent the patent, the less likely Google is to be able to find it. The images are viewable, at least.
I hope that everyone will report this as a bug using Safari>Report Bugs To Apple and will send feedback using
http://www.apple.com/feedback/