FWIW -

You might want to use Performance Monitor to monitor memory usage.  Your variability in execution time may be reflected in memory and/or thread usage by DTS.  We use DTS to load data from various systems into a data warehouse running on SQL Server and had performance issues and ended up moving the various DTS jobs to multiple workstations.  SQL Server was never the issue, but the lack of resources on an individual machine sure was.

Paul Westphal