Can I transfer one Isa AND open another?

I've already put my full £5,100 allowance for 2011 into a cash Isa. Can I still transfer an old Isa to another provider before 5 April?

Source: http://www.thisismoney.co.uk/savings-and-banking/ask-an-expert/article.html?in_article_id=525536&in_page_id=111&ito=1565

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