For anyone interested in this, there is an article in this weeks Science
section of the NY Times. The researchers do not take the cell phone theory
seriously.
There is some evidence of an impaired immune system in some hives, but no
mechanism for this has been found. So it apparently is not just a messed up
navigational system, as the cell phone theory might imply. They do take the
possibility of a problem with genetically engineered plants seriously, but
there are many other things they are looking at.