Autocomplete Random Numbers

I've notice in past month or so that when using Outlook 2003. The
autocomplete will generate random numbers at the end of the name.

For example. If I have a user I send to - (E-Mail Removed), the first time
I have to type it in completely as expected. After that, if I start to type
the name, I may be presented with something like: <JSMIT6395730> instead of
<(E-Mail Removed)>. The strange thing is, if I select the one with the
random numbers in it, it still seems to work.

I didn't pay much attention at first but users are asking about it and I
just don't know why it is happening. I haven't been able to find much out
about it either.

Anyone seen this before and/or have an answer as to why it is happening and
how to stop it. I would guess deleting the N2K file would fix it but I'd
like to find a more practical method than that.

Thanks!