Duplicated articles are aloud but it will hurt your ranking and maybe be looked down upon from Googles stand point.
when they say duplicated they are suggesting that your content is to smiler to another on hub pages, you can have them posted on other sites without getting flagged. they just can not be the same as another on hub pages.
I have had this problem only once and the only thing I can suggest is rewrite the article or re arrange it where it is different by about 50% then you will be OK.
Also if you are using PLR Articles it is always better to rewrite these, mainly because a lot of people will just get them and plaster them everywhere without doing any modification to them.
You could spin them but most spinners come out with a mess of words that make no sense at all therefor making the whole darn thing useless in the end.
Hope this help.