I fully agree with Feydakin. You are asking for trouble if you submit the same article that you have published on your site. I have seen situations where an article was re-published on a site with a higher
PR and higher traffic and Google mistakenly recognized the higher
PR site as having the original article.
Matt Cutts addressed this at one point in his blog. If I remember correctly, he advised everyone to make sure that all of the re-published articles point back to the original site. However, we know that this is a not possible to police and many people who republish articles do not link back to the original like they should.
My advice is to always submit a different and unique version of an article to article submission sites.