Serf internal error 20014 in sporadic bursts

[GoogleCodeExporter]

I have been running modpagespeed on my server for a while now, and noticed that 
at 13:00:49 today, there was a raft of 34 errors in my logs (internal error) as 
follows:

[Thu Nov 17 13:00:50 2011] [error] [mod_pagespeed 0.9.18.7-900 @6186] 
http://www.sellmyretro.com:443/uploaded/img/1933_3_ZX81KBMembrane2008_8dcea_a8d_
505_efaa2_55_d8_3a70_dca4_90cec_3f_6dd02_f5a02_100px.jpg:0: serf_context_run 
error status=20014 (Internal error)
[Thu Nov 17 13:00:51 2011] [error] [mod_pagespeed 0.9.18.7-900 @6186] 
[1117/130051:ERROR:net/instaweb/apache/serf_url_async_fetcher.cc(944)] Serf 
status 20014 (Internal error ) polling for 27: (threaded) (0x2b67b5294370) for 
0.05 seconds

Any ideas on this - the server does not appear to have been overloaded at any 
time...

Original issue reported on code.google.com by sexy.ric...@googlemail.com on 17 Nov 2011 at 2:02