We've had bugs in the past with DTI data, but I fixed the bugs I was able to replicate. If you have a problematic dataset that is free of HIPAA identifiers you could send them to me through a file-sharing site or by email (if it is less than 20MB or so) and I would be happy to take a look. You can find my email by clicking on my name (under Admin) on the main bxh/xcede tools page. If the problem happens with just a few volumes' worth of data, you can just send the subset.