There is an unresolved bug with the SoB client where it does not properly create a 'cache' entry in the registry after being installed. To avoid the problem, reboot after installing and only then let it download a test.
It VERY occasionally drops tests on established installs, and I'm not quite sure why that happens. In either case, you can resume work on your previous test by following these instructions.
1) Identify the test that got dropped by looking in your logfile for a line like:
[Sun Jun 06 10:23:21 2004] got proth test from server (k=55459, n=6312874)
2) Double-check that the test exists as a Z-file in your SB directory. For the test I quote above, the file would be named 'z6312874' - that is, the current n of the test.
3) Open regedit and browse to "HKEY_LOCAL_MACHINE\SOFTWARE\LhDn\sob\cache".
4) Set 'cache' to 2 if it isn't already, and 'k' and 'n' to the corresponding values for the dropped test, using binary values.
5) Save and start Seventeen or Bust - it should begin work on your old test.