texi2dvi instead of pdflatex in R2.7.0? and related bioc 2.2 builds

Dear lists:

I am somewhat puzzled by the use of texi2dvi/pdflatex in R2.7.0. When 
building EBImage (bioconductor) with 2.7.0 I get the same error both in 
Windows and Linux, which reads the following:

** building package indices ...
* DONE (EBImage)
* creating vignettes ... ERROR
/usr/bin/texi2dvi: pdflatex exited with bad status, quitting.
Error in texi2dvi(file = bft, pdf = TRUE, clean = FALSE, quiet = quiet) :
   running 'texi2dvi' on 'AnalysisWithEBImage.tex' failed
Calls: buildVignettes -> texi2dvi
Execution halted

The tex file includes links to png graphics and this might be the 
reason. Running pdflatex on the generated tex file directly produces a 
nice pdf in both Linux and Windows. And this seems have been the default 
in previous version of R.

Now the puzzles are:

1) the bioc build system also uses 2.7.0 and builds vignettes just fine 
on both Windows and Linux:

* DONE (EBImage)
* creating vignettes ... OK
* removing junk files
* checking for LF line-endings in source and make files
* checking for empty or unneeded directories
* building 'EBImage_2.4.0.tar.gz'

2) have the tex settings been changed from 2.6.0 into 2.7.0 as changes 
to vignette have not been significant and the compilation goes through 
fine with 2.6.0.

Or I am missing something and doing something wrong?

Best,
Oleg