EndNote Web CWYW problem

Can anyone help with a problem that some of our students are having
using Find Citation in the EndNote Web plug-in for Word 2003. Although
they have no problem accessing their EndNote Web library from their home
computers via a browser, some of them (but not all) find that they can't
search their library using the Find Citation command from inside Word.
They have no problem doing so on University networked PCs, it's just
some of them can't do it off-campus. The problem doesn't seem to be
limited to a particular Windows or Word version, or to a particular ISP.
The only glimmer of hope is that someone reported that he's solved the
problem by altering his firewall settings so that Word has full access
to the internet. But most of them are just using the Windows XP firewall
with its default settings which appears to list Word as an exception.

Any suggestions? Otherwise EndNote Web is brilliant and the students
love it...

Thanks

Martin Steward
Faculty of Life Sciences
University of Manchester