In a Sage 200 integrated system when you create a new lead then use the option to 'Add or Find this Company' the popup screen will not contain the relevant data from the parent window, the form fields will be blank:

The popup that appears when you use the 'Add of Find this Company' option in a New lead does not pull the data into the form fields.

This is a known error and has been escalated to development.

More information:
As a simple workaround you should be able to use Google Chrome when performing this operation as so far this issue has only been reproducible in Firefox and Internet Explorer.