I faced the same problem when uploading data to my Standard InfoCube.
It turned out that I created my Standard InfoCube by copying from the system-generated APO Planning Area InfoCube (since copying was easier than to create it manually).
However, when copying in this way, system creates an APO Standard InfoCube rather than a BW InfoCube.
If somebody ends up doing the same mistake as me, just delete the InfoCube and re-create it manually, and voila, your DTP will run just fine 