floyd:
One of the big changes going from .3 to .4 was to replace error-return checking with C++ exception handling. The "Empty watch list" exception is thrown by getWatchList() when it completes without finding a non-zero length domain name. There have been changes in the configuration file but they should not have changed the way the watch list is compiled.
Try "topvhost -d" and if you don't see anything other that Input text (the CLF default) then the config file is not being found (probably should be another exception!). Also, cd to the build directory and see if
src/topvhost -vf./.topvhost
lists the logs to be monitored (slightly different info than previous incarnations:domain, log, time-stamp, size).
The only settings that effect the list are 'config_src' (and related config file section), 'file_src' (and related file contents), and 'glob_src'/'gob_omit'
Good luck