Jorge:
I've come up with a couple of things for you to try. It's possible that your NI Application Web Server may need to be repaired. To repair it, go to the Control Panel>>Administrative Tools>>Services, then scroll down to the NI Application Web Server, select it, then click repair to the left.
LabVIEW and .NET Exceptions
http://digital.ni.com/public.nsf/allkb/B15CE9F2715434C386256D3500601878?OpenDocument
Fabián M.
Internal Sales Engineer
National Instruments
