The "matrix" (which is what we usually call it in here) means that each of us is merely a representation of a subroutine running in the greater "program in the sky" most people call reality. Program "synchronism" is not absolute, but rather just a design in the program so that my reality at least appears to be synchronous with yours. If two of us (here in this forum for example) were to stumble upon something incongruous or unexplainable as a "natural behavior" within the program -- that would appear to uncloak this hidden nature of the program -- then the program must next offer at least something in the form of plausible deny-ability.

So, here the program offers the 1918 postulations of Joseph Lense and Hans Thirring known as "Lense-Thirring" effect - otherwise called "frame dragging."

http://www.youtube.com/watch?v=QhwVGKAzPDE&feature=player_embedded#!

I am not saying that any particular video or website, like universesolved or treeincarnation has "all" the answers, but I am pretty sure we are on the right track.

The Wikipedia entry "Pioneer anomaly" has a good, clear discussion of this topic.

To sum up the arguments pertinent here, as offered in the original Physical Review D, Vol. 65, 2002 paper by Anderson and all: There was an apparent anomalous gravitational effect, one not due to the onboard heat sources:

1. By far the main heat sources were small nuclear reactors furnishing electrical power to the circuitry, and they were located at the ends of booms. The antenna was seen nearly edge-on, not as depicted in the link above. The antenna in fact obscured only 1 to 2 percent of the direct line of sight of the reactors.

2. The anomalous acceleration was constant over time, while the heat output of the reactors degraded appreciably as their nuclear fuels decayed.

3. The space probes were spinning slowly about axes through their dish centers. It would seem that any thrust from an unexpected source would not be symmetrical about the spin axis and would disturb the axis appreciably. This was not observed.

Finally, one might consider motivations. The experimenters found the results quite troublesome, perhaps embarrassing. Explain them away or open themselves to questions concerning their competence -- strong incentive, it would seem. They chose to present them, and in detail for anyone to examine.

Are the Pioneer experimenters correct? Who knows? Place your bets and wait and see.

Reference paper is: arXiv:1107.4987, 2011 - arxiv.org
"Many attempts have been made to find a conventional explanation to the Pioneer anomaly as a systematic effect either related to the probe itself, allowed by a loss of energy from power generators on board, or to the environment of the probe, due to the presence of dust or gravitating matter in the outer solar system. These have been followed by sustained efforts for recovering further data and performing new analyses covering the whole Pioneer 10/11 missions. Up to now, these attempts have remained unsuccessful in explaining the totality of the Pioneer anomaly.
"Furthermore, a recent study, confirming the secular part of the Pioneer anomaly, has also analysed the modulations apparent in the Doppler data, showing that their frequencies correspond to the Earth’s motions, and that the Doppler residuals can be further reduced by introducing simple modulations of the radio links. Modulated anomalies cannot be produced by a conventional explanation of the secular part but require a further mechanism (trajectory mismodeling, solar plasma effects, ...) to be accounted for. On the other hand, simple models modifying the metric are able to reproduce both types of anomalies. These features leave the possibility of a common gravitational origin of the Pioneer anomalies, pointing at a deficiency of GR occurring at length scales of the order of the solar system size."