I use SQL Nexus all the time to identify bottlenecks of my SQL Servers and I absolutely love the tool. I ran into a small issue though where I could not always load the *.trc files. It would start and fail very quickly and move on to importing the other data. While the tool was still useful it was not as useful as it is when the *.trc files import correctly. With them I can dig in and see the actual queries that were causing the issues. I found that the problem was my own. When I launched SQL Nexus I would create a new database for my traces and I would put a ‘_’ in the database name. It does not cause errors and is a valid database name but as soon as I took out the ‘-’ all my *.trc files will import with now issue.
hope that helps and happy troubleshooting