One Firestats install, 3 websites, one working?

[Erik Harris]

I've got three WordPress sites on three different domains: kungfu-
silat, glutenfreegoodness, and harriswholehealth (HWH), all .com
running one copy of FireStats (itself on a fourth domain,
eharrishome). Of the three WP sites, two belong to my wife (she runs
them, I do the technical site management), one being her personal blog
and the other being her business (HWH).

Lately, she's been noticing that the HWH site has been reporting
_really_ low numbers for daily visits and views. Low, but not zero.
It might be reasonable to suspect that visits have just plummeted, but
she's received a number of emails through the site's contact form, so
she knows there are considerably more visitors than are being
recorded. I also tried visiting the site myself from another browser
(so that I wouldn't be logged into the site and therefore not
counted), even going through a search engine to find the site.
Neither the visit nor the search engine referral showed up in the
site's Firestats log (checked immediately, and re-checked after about
20 minutes). The other two sites are reporting figures that seem
entirely reasonable.

This isn't much info to go on to troubleshoot the problem, I know, but
can anyone give me some ideas at least on where to start? I noticed
that the Firestats site footer was turned off for the affected site,
and I've just turned it back on, but there's no reason that should
stop it from working. The site is also using an entirely custom theme
which has not undergone any changes since it was last working as
expected.

I could install a separate stats plugin to see how far off the two are
from each other, but that would really only answer the question of "is
it reporting accurately?" Given that the answer is already pretty
conclusively "No," that doesn't seem like a very useful step.

FireStats is version 1.6.2, all three WordPress sites are running
2.8.4, and they're running on a LAMP server in a shared hosting
account from HostGator (all four domains, the three WP sites and the
domain that FireStats is installed on, are on the same HostGator
account).

Any help would certainly be appreciated.