[Serusers] SIP Accounting Module problem

Hi folks, I'm trying to get my accounting services working, but am having trouble doing so... I am using the sample ser.cfg file, and am having a problem loading the acc.so module. In the ser.cfg file, I try added the line: loadmodule "/usr/sfw/lib/ser/modules/acc.so" to the bottom of the loadmodule section. I haven't done any modparam or scripting yet, even so, when I restart the ser service, I get: Starting SER : cat: cannot open /var/run/ser.pid. If I comment or remove the loadmodule line, ser will load again. Is there anything else I need to add or configure before loading this module? I went to /usr/sfw/lib/ser/modules to make sure acc.so is there, and it is. Any help is greatly appreciated. Thank you very much. Ben