You are certainly running with a minimum of RAM but whether this has anything to do with your problem I don't know. Insofar as your copy of AVG is concerned, it conforms with the Grisoft's system requirements although the current version of AVG Free is 6.0.655 with the current database being #420 released on 8 April; suggest you consider updating.
If you have followed the Universal E-Mail Scanner's installation instructions, you will find an excellent Help file, Avgemc.help, in the Grisoft>AVG 6 folder in your Program Files Directory that includes a detailed explanation of how to configure both AVG & OE.
Also, the image in the attachment which I have included with this post, shows my AVG Control Center opened at the Mail Proxy page; on the right hand side of the pic. is a 'Configure' button that leads to Scanner Setup which incorporates a very helpful Setup Wizard.
Follow the help file instructions and the wizard and you should be right.