Hi please give this a shot:

In Tools, Options MAIL FORMAT tab on Signatures, make sure you
signature is selected for Signatures for account:....
Signatures for replies and forwards.

Also check at top of this box if "Use MS Word 2003 to edit email
messages. If yes them open MS word, go to Tools Options and general.
under Email settings you will see signature information there. make
sure you have an actual signature text in the lower box and that it
contains someting. I have seen cases where people name a signature but
it has no content. Putting a blank signature in emails.

Close and restart Outlook and word to refrsh settings after these
changes are made.

Hope that helps.