Unable to display user selection dialog

[Topher]

Whenever modifying users on a share (or anything that needs the user selection dialog box) I get

"Unable to display user selection dialog

(null)
"

Note that I don't get any other assertions or anything about an Object Picker.

Any know how to remedy this?
Thanks in advance...


1) Version of XP
XP - SP1
2) Hardware setup
Athlon 1900 XP, 512 meg DDR
3) What exactly happened leading up to the problem
Click the "Add User button" when modifying users on a share.
4) Exact error messages
Above
5) Any antivirus, firewall software you are running
McAfee 4.5

[Topher]

I fixed this with a little help from:
http://www.annoyances.org/exec/forum/winxp/r1077080913

"please check your riched32.dll file in system32 directory. it must be 3.5KB and you can copy from original xp cd-rom. try and enjoy!"

Actually the original on my disk was 2kb, but the one on my machine was 170+k, probably replaced by a notepad replacement tool I had installed.