The first button does cause a java script error
VISTA sp2
IE 8.0.6001
Webpage error details
User Agent: Mozilla/4.0 (compatible; MSIE 8.0; Windows NT 6.0; Trident/4.0; SLCC1; .NET CLR 2.0.50727; Media Center PC 5.0; .NET CLR 3.5.21022; .NET CLR 3.0.30729)
Timestamp: Sun, 31 May 2009 16:46:54 UTC
Message: 'style' is null or not an object
Line: 2252
Char: 5
Code: 0
URI: https://gatekeeper.astarobeta75.com:4444/qm/jape/jape_prereq_10_prototype.js
Upon further investigation, the popup window does open if you ignore the error but does not close even if you go to a different page in mail manager unless a date is picked.