I have been doing some learning on this today. It seems that SSIS is FAR more picky than DTS ever was about data types. SSIS seems to refuse to do any processing unless the data types completely match.
Now I can see their point that you dont want to fail the process on the 4,999,999 row out of 5,000,000 but it is very frustraiting when the data is fine but the data types have been defined differently. Unicode types seem to be the main offender here.
Once again it may just be me