> I would like to know whether TeTeX 3.0 did introduce some change in DVI files > related to Forward Search.
I am not aware of changes in this respect. I recommend to compare the settings about source specials in your texmf.cnf file (default is off in teTeX-2 and teTeX-3). If you are using srctex.sty, compare the two versions. Also, compare the resulting dvi files with some tools that shows all specials to you (e.g. dvitype). If all fails, write a mail to the tex-k list (see tex --help). Thomas