[Microsoft][ODBC Excel Driver] Cannot open database '(unknown)' : DOTNET

Here's the error message:

[Microsoft][ODBC Excel Driver] Cannot open database
'(unknown)'. It may not be a database that your application recognizes,
or
the file may be corrupt.

My setup:

I have a Windows Service on XP that runs under admin user.
I copy an excel file to a folder.
I use Diagnostics.Process to start a third party process
RXImportExport.exe with parameters.

This RXImportExport.exe export data from a SQL Server 2000 database to
the excel file i've just copied.

When I launch the process, i get the error message from the log
function of the RXImportExport.exe.

If i leave my process running-continue and take the parameters and
launch the .exe from a dos prompt it is working properly and data gets
exported.

-------
Could it be that the file being copied is still on "hold" by the
operating system.
Could it be permission related?

I really have no clue anymore.

I could write a novel of the thing i've tried.

One other thing, it is working sometime!

I've tried to launch it from a batch file since it was working from DOS
prompt.
I get the same behavior-error. If i launch the batch file manually, it
is working!

Any help would be appreciated.

Thanks