Would you mind posting a link to your form so that we can investigate?
I am helping Shannon out with this one. I'm sorry to hear you are having problems.
I have tested your form, but everything looks fine from this end.
Can you provide some information about the users who are experiencing the problem? What operating system are they using? Windows 7? Windows XP? Mac? What browser and version are they using?
Try closing all instances of the browser, open the browser, clear the browser cache, and reload the form.
Try another browser.
Can you provide a screenshot of the form when the user experiences the problem?