Here are a few of things to check:

- Does IC pass data integrity?
- Is anyone in IC when you try the upgrade?
- I have heard in some network environments that having 2-character extension can cause problems. Try temporarily renaming the data extension to 3 characters to to the upgrade (you can put it back afterwards if you choose).
- You may also want to attempt the data conversion with the data copied to a local drive, eliminating the network environment part of the equation.