Strange error message

Lately, I'm getting about three e-mails a day a sent from my Apache
server, with no subject line and with the following message body:

Subject: SkunkWeb critical error, host soundience.com
SkunkWeb: error reading stdin from client

That's it. No more information in the e-mail or logs at the time of the
messages. I'm running several virtual hosts behind Apache, and the
message does not indicate which virtual host or page is causing the
problem. The web sites seem to be working okay on casual inspection, so
perhaps it's benign.

Has anyone encountered this? Any suggestions on how to track down or
correct the errors?

Cheers,
Andreas


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