pdflatex doesn't work any more after switching to miktex 2.5 with texnikcenter and lyx

[Marius Disler]

Hello

I have installed miktex 2.5, but now pdflatex doesn't work any more with 
texnikcenter and lyx. I get the following error message in Lyx:

"The file doesnt exist: c:/..../temp/lyx_tempdir/.../newfile.pdf"

I tried out several versions of LyX. Not one works. ps2pdf and dvipdfm 
work, but I need pdflatex because of formatting problems with the other 
options. pdflatex with Miktex 2.4 worked fine.

I'm thankful for any help.

Regards, Marius