Copying from Excel then opening email to paste into causes..

This issue has popped up over the last week or 2. When I copy some cells
from Excel, then open a new Outlook email to paste said data into (by
selecting new/forward/reply), Excel instantly crashes - it just disappears.
When reopened, it shows the list of last saved/Autosaved open documents, like
after most crashes. The issue doesn't arise if the new email is opened
before the Excel data is copied (ie if I remember to do so!). The size of
the data isn't an issue - maybe 20 cells' worth of unformatted figures. If
the email is brand new then all it contains is my work signature, so there's
no size issue there either. Here at work we use Windows and Office XP, with
(as far as I'm aware) the latest updates installed (SP3, etc). Is there some
bug causing this that I need to fix?
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Thanks in advance - reg o.