I can duplicate the problem in IE8 here - although not in IE9 (IE8 mode) which suggests it's more of a bug in IE 8 than anything else.
I've also checked the output from the server, and it's identical in both cases. Indeed in IE8 if you press a F5 on the "blank tab" the report generates again, and displays.
I'll keep on the lookout for a work-around, but so far haven't had much joy.
One thing that did work was changing from a button to a string (ie a hyperlinked string). I did have to make a small tweak in 5.30 to make this work right - but then that did work.
Cheers
Bruce