> I've been wondering if the CCD problem could be related to a  
> directional disorder so bees can not find their way back to the  
> colony. Do bees ever depend on magnetic field lines for direction  

There was speculation about this for quite some time, as bees 
clearly do have some detectable iron in their trophocytes.
See http://jeb.biologists.org/cgi/reprint/126/1/375.pdf


But one can't get the bees to show that they use any sort of
magnetic-based navigation at all.
See http://jeb.biologists.org/cgi/reprint/86/1/1.pdf


Also, be aware that the statements made in the first paper above
about bees building combs in alignment with magnetic fields or
compass points has been debunked multiple times, as the bees
build their comb in the direction of whatever attachment "bar" is
provided, and if a solid sheet is provided, they will build comb
pretty much "at random".

Ian Rumsey did a series of articles in the Apis-UK newsletter documenting
a test he did, which produced the usual of apparently encouraging
easy-to-misinterpret results mixed with utterly random acts proving that
the bees pay little or no attention to the earth's magnetic field:

See http://www.beedata.com/apis-uk/newsletters05/apis-uk0905.htm 
(The article series about his tests starts several issues before this one.)

> and, if so, are magnetic field lines changing or becoming unstable  
> possibly leading to observed problems?

If the Earth was to reverse its magnetic field again (which has
happened several times, as shown in the geological record)
I think that we would have noticed. For one thing, the yells
of "WTF?" from every Boy Scout and sailor on the planet would have 
alerted us to the problem.

As far as "unstable" goes, there are minor variations in the strength
of Earth's magnetic field, and the overall field/flux varies in a
detectable amount in the normal course of events.

But not to worry, Earth's magnetic field is not all fluxed up.

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