I was clicking about, trying to add some clipart to a Word document.  Did the "Office online" search on the side taskbar, and the whole app hung.

Seems Office 2003 doesn't handle web proxies properly.  I went into Internet Explorer 6 SP2 and disabled the HTTP proxy I had specified for my ISA Server and it went fine.  I suspect it had to do with the Integrated authentication that ISA uses to verify user credentials at connection time across the proxy.  Strange.