Answer: This may be due to some problem that affects the normal ability of the Foxhound Monitor to reconnect to target database(s) in order to resume sampling when Foxhound is restarted. This is not an expected situation: even if Foxhound can't connect to the target databases it shouldn't become unresponsive.

In order to get Foxhound to respond so you can figure out what's going wrong, you can suppress the automatic reconnection process by starting Foxhound in "safe mode", also known as safe startup.

Here is an example of this scenario: A Foxhound Monitor session used the SQL Anywhere 11 ODBC driver to connect to a local SQL Anywhere 8 target database server on a Windows Vista system where no SQL Anywhere 8 ODBC driver software had been installed. Not only did Foxhound become unresponsive, but restarting Foxhound didn't help until sampling was stopped by using safe-mode startup.

See also...
How do I start Foxhound in "safe mode"?
How do I start Foxhound in "debug mode"?
How do I see Foxhound diagnostics, errors and exceptions?