Why does right-clicking in Outlook sometimes not bring up spelling corrections?

You know how in Outlook 2002 and 2003 you get a red line under words
that you mispell.  You can then right click on them and pick the
correct word.

A strange thing keeps happening to me.  Once in a while, on some
emails (and not others) I go to right-click and instead of offering
spelling corrections it just offers to paste in my one of my email
signatures.

This hqappens on HTML emails only.  But it is so intermittant.  It is
also ver frustrating.  The only way to get ride of it is to convert
the email to plain text, and then back to HTML.  When you do this, you
have to copy/paste the text since converting to plain text wipes out
all your text, More Microsoft brilliance!

Any idea why sometimes the righ click brings up signatures and most
times it does what it should and offer spelling corrections?

Any idea of how to fix this prob (short of using just plain text emails)?

thanx in advnce