I had same problem.
True Combat Elite empty cd key.
I downloaded ET_PBSETUP.EXE then I can play now.
Go here, download ET: PunkBuster Setup + KeyGen.
http://www.te666.com/site/index.php/donloads/patches/1676-et-punkbuster-setup--keygen.html
or click here to start download ET_PBSETUP.EXE.
http://www.te666.com/site/index.php/donloads/patches/1676-et-punkbuster-setup--keygen/download.html
link corrected. thanks for reply.