I have the same problem too. The Server validation error messages in IE8 will not show when the form runs inside a frame. However, if you turn your Cookies and Session Cookies in IE8 on it works in IE8 too.
Since Cookies and Session Cookies are turned off in IE by default a lot of users get a bad user experience when the form runs inside a frame.
Does anybody have a workaround ?
I have a newly created form that runs inside a frame on live URL here:
I'm also attaching my source file so you can have a look at it.
The validation error messages for the text and textarea fields works because of the client side/spry validation, but the error messages for the file fields will not show because they are server validation only.