MSNBC has this article that may explain today's data problems.

A thunderstorm in Australia disrupted science work on Mars, where the Spirit rover was waiting for instructions to study a rock, NASA said Wednesday.

Controllers were supposed to beam commands to the rover through a Deep Space Network antenna in Canberra, but rain and lightning made for a weak signal, and “it actually didn’t get all the data,” said mission manager Jennifer Trosper at NASA’s Jet Propulsion Laboratory in Pasadena.

Instead, Spirit continued to use a day-old sequence of commands that kept it awake and communicating but not moving or using its instrument-tipped robotic arm.

Don't know about Pathfinder. Perhaps it had trouble keeping a high gain antenna properly pointed at the Earth, but that's just speculation on my part.