Send to Mail Recipient (as attachment)- Excel 'not responding'

I am getting a lot of grief from almost 100 users because in the past couple
of months the Send to Mail Recipient feature has stopped working reliably in
Excel 2003.

We are using Office Professional 2003 (Excel and Outlook 2003- connecting to
an off-site Exchange server). They are all running on Windows XP SP2 with
all of the updates. I am also running McAfee AntiVirus; some machines have
Enterprise Edition 8 and some have 8.5.

When the user chooses the Send to Mail Recipient (as attachment) option,
Excel freezes. Task Manager shows 'Not Responding'. Often, if you End Task
and re-load Excel, the sheet can be recovered, and almost always sends the
second time with an error.

Typically Outlook and IE7 are running in the background when this error
occurs. It is an intermittent problem so I have not been able to figure out
a way to recreate the error on demand. But it happens often enough that I
get one or two complaints every day.

I hope that someone can offer advice. Thank you.