I am in absolutely no position to judge the technical execution of this work, but a group has posted a possible solution to the "Pioneer Anomaly" on the Physics/Astronomy ArXiV server (http://xxx.lanl.gov/abs/1103.5222). For those who haven't been following along at home, there appear to be subtle unexpected Sun-ward accelerations (i.e. higher than expected decelerations) seen in the Pioneer 10 and 11 spacecraft while leaving the Solar System. Sean posted an earlier discussion of the anomaly and a possible reported solution that does not involve modifying gravity. However, this latest paper is by a different group, and posits that reflections within the spacecraft are enough to explain the discrepancies. There's a nicer write-up than this one at the Technology Review Physics ArXiV blog. FYI, it was posted a few days ago, and is not an April Fool's posting. Also FYI, my kids just got passports, and did you know that there's an image of Pioneer 10 on the inside back cover? Beamjockey did some nice sleuthing a few years back and dug up the source image!