We are trying to scan on a windows 2003 terminal server. The twain_32 directory is copied to the windows path of every terminal user, but no scanner is found. Not even the Administrator account can find the scanner. The scanner  works in microsoft office but not with Atalasoft.

When testing on a windows 2003 non-terminal-server (small business) everything works fine.

(Remark: the scanner is visible from the server, it is connected as a local twain scanner. I am NOT trying to scan with a scanner connected  locally to the client computer)

Any suggestion ?

Microsoft Office might not be using TWAIN.  Can you please download and install IrfanView?  It's a free product that definitely uses TWAIN for scanning and doesn't use Atalasoft, so we can see if the problem is with TWAIN or with our DotTwain.

http://www.irfanview.com/

Irfanview didn't find any twain drivers either. 

After running dottwain, I found the following files under ...local settings\temp\

twunk002.mtx
twunk001.mtx
twain001.mtx
TWAIN.LOG

Twain.log contained the following:

TWAIN_32.DLL - MESSAGE - CTwunk  ::AppInitialize - Reset Log

TWAIN_32.DLL - MESSAGE - CTwunk  ::OpenServer - Starting Thunker

TWAIN_32.DLL - MESSAGE - CTwunk  ::CloseServer - Why Can't We Find The Thunker Window?

TWAIN_32.DLL - MESSAGE - DSM     --DsmEntryDiagExit (RC = 0, CC = 0)

TWAIN_32.DLL - MESSAGE - CTWTRACE--DotTwain(3) to NULL:

TWAIN_32.DLL - MESSAGE - CTWTRACE--CONTROL, IDENTITY, GETFIRST

TWAIN_32.DLL - MESSAGE - DSM     --DsmEntryDiagExit (RC = 1, CC = 0)

TWAIN_32.DLL - MESSAGE - CTWTRACE--DotTwain(3) to NULL:

TWAIN_32.DLL - MESSAGE - CTWTRACE--CONTROL, PARENT, CLOSEDSM

TWAIN_32.DLL - MESSAGE - DSM     --DsmEntryDiagExit (RC = 0, CC = FFFF)

DotTwain gets a list of drivers from TWAIN and the log you provided shows that TWAIN can't find any drivers.

After a little searching it looks like TWAIN is not compatible with terminal services and suggest using RemoteScan.  They created a custom version of TWAIN that works. 

Another possible solution was to modify the registry; you might try this suggestion first.  Here is a link to some information on it:  http://www.brianmadden.com/Forum/Topic/85531

The registry hack worked ! - though I found out myself just before you sent the link.