Oracle Database Express Edition (XE)

I have created a 11g XE database manually on a windows 2003 R2 server - 32 bit. I have also installed XDB on it manually.

I have validated the XDB install by executing

Select comp_name,status,version from dba_registry the output of which is :-

COMP_NAME STATUS VERSION
Oracle XML Database VALID 11.2.0.2.0
Oracle Database Catalog Views VALID 11.2.0.2.0
Oracle Database Packages and Types VALID 11.2.0.2.0

There are 0 invalid objects.

I have a package which uses UTL_SMTP in order to send out emails.

I am trying to add an ACL as required by Oracle 11G for UTL_SMTP to work. The code i am using for this is

BEGIN
dbms_network_acl_admin.create_acl(acl => 'mailserver_acl.xml',
description => 'Email permissions for App',
principal => 'MYUSER',
is_grant => TRUE,
privilege => 'connect');
END;
/
However, this above code when executed gives me an error

ORA-46105: Unable to load security class DAV::dav
ORA-06512: at "SYS.DBMS_NETWORK_ACL_ADMIN", line 252 ORA-06512: at line 2

I have tried un-installing XDB and re-installing again but to no avail.

Does anyone with experience in Oracle know if just installing XDB is sufficient for creating ACL's or are there any other dependencies that i also need to install?