How to enter usernames and passwords when aperars an error "Text expected!"

How to enter usernames and passwords when aperars an error "Text expected!"

  
I had built an aplication with an login screen (Username, password and Domain), and the enter fields are text type, but when i enter data in there this error apears "Text expected!", but the the strange thing is that this error only happens in some computers, in others doesn't happen, and the aplication runs perfectly.
I also checked my internet options and they are the same of the other computers.
Does anyone can help me??
Hi Anibal,
can you post a small espace with the described behavior?
Have you checked the input's "Is Mandatory" property and the button's "Validate Inputs" properties?