There is a problem in the CSS. Heres the fix.
#shadowbox_title {border: 0px solid;}
#shadowbox_info {border: 0px solid;}
Add it to the css your using to theme shadowbox and life is good.
Webpage error - Invalid Argument;
Invalid argument. shadowbox-base.js, line 136 character 21
User Agent: Mozilla/4.0 (compatible; MSIE 8.0; Windows NT 5.1; Trident/4.0; .NET CLR
1.1.4322; .NET CLR 2.0.50727; .NET CLR 3.0.04506.30; .NET CLR 3.0.04506.648; .NET CLR
3.5.21022; InfoPath.2; OfficeLiveConnector.1.3; OfficeLivePatch.0.0)
Timestamp: Fri, 27 Mar 2009 20:34:27 UTC
Message: Invalid argument.
Line: 1
Char: 1039
Code: 0
URI:
http://mjijackson.com/shadowbox/build/adapter/shadowbox-base.jsMessage: Invalid argument.
Line: 1
Char: 1039
Code: 0
URI:
http://mjijackson.com/shadowbox/build/adapter/shadowbox-base.jsMessage: Invalid argument.
Line: 1
Char: 1039
Code: 0
URI:
http://mjijackson.com/shadowbox/build/adapter/shadowbox-base.js