Squid3 with esi: ESI subrequest failed transfer

We are trying squid 3 as a reverse proxy with ESI.
This is the error in the log when I try to visitate an ESI page on my
CachePeer:

ESI subrequest failed transfer

This message is reported 3 times, because our esi page import 3 php pages.

We have a cache peer on the same host of squid, but obviously on another port,
squid is configured as a reverse proxy with esi.

Apache is configured to add this header only on esi file:
Surrogate-Control max-age=60,content="ESI/1.0"

Moreover, the browser that ask squid for the esi page can see the result of
the assembled page only once.

What does the above error mean?

Ciao, Dino.

-- 
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|  Dino Ciuffetti - Network Administrator  |
|      +**+   Pro-Netics S.r.l.  +**+      |
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