SQL & PL/SQL

I am using the SRW package in 11.2.0.2.0 to call an Oracle Report on our Reports Server (10.1.2.0.2). I get an ACL error when trying to do this.
The debug of the SRW package shows:

(...)
Starting run_report: building url
*** Building URL (RUN_REPORT)
OK : URL built : http://...
*** Submitting HTTP Request
*** using URL :http://...
ERROR : HTTP request failed

The backtrace shows:

ORA-20212: 
ORA-06512: at "PROD.SRW", line 648
ORA-29273: HTTP request failed
ORA-06512: at "SYS.UTL_HTTP", line 1819
ORA-24247: network access denied by access control list (ACL)

The ACL is configured for the user that runs the code, and running the report without SRW does work.
If I copy-paste the generated URL directly in the UTL_HTTP.request it works (running this code as the same user):

set scan off
declare
  v varchar2(4000);
begin
  v := utl_http.request('http://...&statusformat=xml');
  dbms_output.put_line(v);
end;

Results in:

<?xml version = '1.0' encoding = 'ISO-8859-1' standalone = 'yes'?>
<serverQueues>
   <job id="11" queueType="past">
      <name>SMRVZB.rdf</name>
      <type>report</type>
      <status code="4">Finished successfully </status>
etc.

Any idea why I get the ACL error when using SRW and not when using UTL_HTTP?

Ino