Resolution:
The "buildBPMRepo" utility creates a Repository file for BPM from a blank repository file. For sucessful BPM operation, the repository file must contain the BPM framework (custom task and other related diagrams).

So you can either use bpm_default.dat(provided with the BPM installation) OR create one using "buildBPMRepo" utility which is provided in the "bin" directory of the BPM installation.

You can use the buildBPMRepo utility in the following way -
buildBPMRepo  default.dat, where default.dat is the empty dat file in which you want to import the BPM related stuff.