Ok, I got the error.
I have found an article on the internet http://forums.asp.net/t/1132582.aspx where it explains that a similar error was showed up after installing KB928365 patch.
I have not seen that patch installed on my server so I started to uninstall components from latest installations.
Finally, I got that Microsoft .NET Framework 2.0 Service Pack 1 was causing the issue. After uninstalling SP1 and rebooting the server the error was not thrown anymore. When running a scan on the server, it has showed that KB928365 was missing and pending for installation.
I have reinstalled Microsoft .NET Framework 2.0 Service Pack 1 just to confirm the error. And it blew up again. One interesting thing was that I have run the scan again and KB928365 was not missing. Maybe it is "included" in Service Pack 1.
Can someone from Captaris tell me how to solve/avoid this issue? Updates are automatically installed on the servers in the whole company and we are getting unexpected errors because of this issue.
Thanks,
Juan