I suspect the problem you are having is because the data is being reloaded with the specified free space parameters. As the partition was (almost) full it is probably that you now can't fit data plus free space into the partition.
The v7 and prior "correct" way of doing this is to
1) ALTER partitioning-index PART n VALUES(new-high-values)
2) REORG TABLESPACE
In V8 it depends on whether you you using table or index partitioning.
In your situation, I would
- recreate the original tablespace, table and partitioning keys, with both FREEPAGE and PCTFREE set to zero.
- reload your unloaded data
- alter partitioning keys, freepage and pctfree.
There are other things to investigate - eg converting to large partitions with DSSIZE but you can't do this with a reorg.