Hi Malai!
first (and easy) possibility: maybe your vdr uses a remote.conf made for lirc. Try to delete (or rename) the remote.conf file in either /video- or /etc/vdr (or whereever your vdr-config-files are located)...
Second possibility: vdr is run with --no-kbd option - just leave it away.
Third possibility: your vdr is compiled with NO_KBD=1. If so give a second compile a chance...
The next questions would be easier to answer when you supply more informations wether you compiled vdr yourself, used a debian archive, etc.
Greets, MaX