Ok , I had this problem also , Not sure if your in an office enviroment or
not , But i looked all over the web and could not find a fix for my user. So
what i did was this
I made the User a Signature in My own personal Outlook on My PC , and then
from there i went in to his Outlook on his PC went to My computer/Docs and
settings/{the users file/profile}/Application Data/microsoft/Signatures And
deleted the 3 files located there for his signature. Then i went back to my
PC And opened a new Email and attached the 3 Files i made for his Signature
{in my outlook} Whice were located My computer/Docs and settings/{my
file/profile}/Application Data/microsoft/Signatures { its like a word doc, a
notepad doc, and a html file}
I attached the ones i made from my outlook to the Email and sent the email
to the user. I then went to his desk and open the email i sent , and saved
the Files attached, to his My computer/Docs and settings/{the users
file/profile}/Application Data/microsoft/Signatures then went into his
outlook Tools/options/mailformat/Signatures and selected the signature for
send and replys .. Opens up a new email and BAMMMMM the  was gone. But if
at anytime i went back into Edit a signature .. Sure enough that  would
come back and i would have to repeat process from "" I then went to his desk
and open the email i sent , and saved the Files attached, to his My
computer/Docs and settings/{the users file/profile}/Application
Data/microsoft/Signatures then went into his outlook""
Email me at (e-mail address removed) if this worked for ya ... Later