Login problems are usually due to cookie problems with your browser. One member worked around the problem by using a different browser but the real answer is to delete the Yuku cookie if you know where to find it, otherwise you may need to delete all your cookies.
You may like to browse the full Yuku Member Support forums too:
If you decide to open a support ticket with Yuku, go here:
and when you fill in the form the Board URL is http://whirligigtv.yuku.com