Zero Sized Reply Error when accessing PHP scripts from Apache

[Lynux]

Apache suddely started giving me a strange error message
When trying to access my php scripts:
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ERROR
The requested URL could not be retrieved

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While trying to retrieve the URL: myURL

The following error was encountered:
Zero Sized Reply
Squid did not receive any data for this request.

Your cache administrator is webmaster.
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Anyone have any idea what is causing this??

Thanks in advance ! =================================
Imagination is more important than knowledge.
(A.E.)