I just this morning dealt with the same issue. The package I was attempting to install was a design time package: dclDragDropDR103R.bpl. The problem I had was that the design time package required the run time package, a common requirement, and when the run time package was compiled, for some reason, it was not written to $(BDSCOMMONDIR)\bpl. I manually copied it there and the design time package installed just fine. I have not figured out why it was not written there to start with, but this fix will work for me for now.