Are you sure that Expression can process code in that way? It may be that it doesn't work in Preview but does work when published.
Another advantage to publishing is that you can view the source to see whether Expression has added anything that is messing around with the Email Form.
Yes it should work in preview - same as frontpage. However I published the one page with the e-mail form and received the same results - screen blinks and blanks out fields.
I am building the pages using a Dynamic Web Template (.dwt). As a test I built a page without the template and it works just fine in preview as well as after being published. It appears that the .dwt is the culprit. At least I now have a work around. If anyone has info on why the .dwt would have an impact it would be appreciated
