Wierd timeout with apache mod_proxy


I may have posted this in the wrong place: apologies if I have. I currently have a setup with Apache proxying requests to mongrels. Occassionally, in the apache logs I get an error that looks like

[Tue Oct 30 12:00:28 2007] [error] (70007)The timeout specified has expired: proxy: pass request body failed to ( from () [Tue Oct 30 12:00:28 2007] [error] [client] Handler for proxy-server returned invalid result code 70007

Does anyone know if this is an Apache/Mongrel issue, and why the timeout could be occurring?

Thanks in advance for anyone's help