DTS Erroring On Index In Unicode Conversion

I have undertaken the following process to convert a database to unicode support. This is sql 2000 SP4

- Create a new database dbnew
- Script the old database dbold with all objects, everything, and dependencies
- Global replace varchar with nvarchar (etc etc) in the script
- Execute the script to create all objects into dbnew
- (Objects all exist fine)
- Startup DTS and choose olddb as the source, newdb as the destination
- On DTS step 3 choose "Copy Objects and Data between Sql Server Databases"
- Untick "Create destination objects"
- Change copy data to append data (all tables in dbnew are empty)
- Tick copy all objects
- Untick "Use default options" and clear every option (so hopefully we are only copying data)
- Click next and run

DTS gets through the first "phase" to 100% but then it fails on a duplicate key error on a table that has a unique key on its (now nvarchar) description field

Yet in Query Analyser I can do "insert into failingtable select * from olddb..failingtable" and the data comes across fine.

So why is it failing in DTS ? And are there any other options or settings I can try ?

thanks