Unexpected error when using a distribution list

[rsw]

I have a user who has a large distribution list and is trying to send a
message using the distribution list and is getting an unexpected error.


I had him send me screen shots of the errors.
The first screen shot said Microsoft Word in the title bar and then
said An unexpected error has occurred.
I had him turn off Word as the default editor and restart the computer.
He tried again and got the same error except in the title bar it now
said Microsoft Outlook.

He says that this error completely stops him from sending the message
to the distribution list.

I first thought the size of the distribution list and checked with the
Administrator and he said that is not an issue as there is no limit set
on Exchange. He also stated that our company has many DL that are
hundreds of contacts and those all work fine.

This is an outside user who works from his home over a VPN.

I am thinking it may be something with a contact but I am just not
sure. He cannot bring in the computer until December.

I just thought if anyone out there has run into this issue before you
could guide me in the right direction.

Thanks