[CentOS] ClamAV help needed

ClamAV is installed on my CentOS box. I edited the conf file and assumed all is well. Clearly it isn't.

Every day I see in logwatch that my signatures are updated, and the database notified, but if I try to scan a file manually it tells me that my signatures are 55 days old.

I tried looking at a how-to, in the hope of identifying the problem, but it is hopelessly out of date, and I reached the stage where it seemed that following it any further risked my installation.

Can someone please give me a quick run-down of the things I should check. Clearly freshclam is running, but that's about all I know for certain.

Thanks

Anne