"Please enter your name" in customer registration, error

I use esport template, joomla 2.5.2 and viruemart 2.0.4
When a customer try to register in checkout although has fill all required fields (first name, last name etc...) an error message appears on top of the page "PLEASE ENTER YOUR NAME" and customer can't continue to check out!

See attachment

Any idea?

Thanks in advance!

Hi

That's odd I do not have such problem on my copy. Please show me Your site.