Upon loading topspin, it will take a little time to load up the spectrum that you used last time. If you type dir when the screen is still blue, you will confuse topspin.
To solve the problem, go to File -> Open, and find the path that contains your data. It is usually /opt/topspin/data/[your login]/nmr. Open any data file. This will reset the default data file path to your own directory. If you type dir now, you will be able to see your directory.
If it seems to take quite long to load up the last data file once you start topspin, it is likely because you have too many data files. Delete some!