checkout validation - billing information fields will not validate

[JBWH]

Not sure if this is thright board so please show pateince.

I am having an issue in the checkout with the follwoing error even though the fields are populated 

The first name cannot be empty., The last name cannot be empty., Invalid email address ""

I dont really want to remove any validation but I do not know where to start to try and resolve this issue.

Is anybody able to offer any assistance.

Thanks you for your patenice and your help.

Regards

[dametrics]

Can you post a link to your site? Hard to troubleshoot without being able to check if something is missing.

[taxlandinfo]

I have a similar issue when I enable the 'Checkout for the Guests'.

One of my online stores (Magento 1.9) works normally, you can register in the web store, log in, order products, etc. But if I 'Allow Guest Checkout' and I try to order as a Guest, the same error message appears on the Checkout page:

The first name cannot be empty., The last name cannot be empty., Invalid email address "".

The fields are filled correctly of course. I have tried to find solution for this problem on the internet, I Googled it, but I did not found any useful thing.

The settings are:

   SALES / Checkout / Checkout options

      Enable Onepage Checkout: Yes
      Allow Guest Checkout: Yes
      Enable Terms and Conditions: Yes