spamassassin not working

If "standalone program" is selected in the spamassassin settings, then spamassassin fails to work. This has changed recently (within the last two weeks) and clients began complaining that no spam was being detected. Changing this setting to "spamc client" has fixed the problem, but I don't understand why this has changed and why the standalone program is not working. Is there someway I can test if the other settings are correct?

Status: 
Closed (fixed)