Hello Philippe,
What version of LabVIEW Real-Time are you using? When did this start happening?
What version of NI-VISA do you have installed on the real-time target?
If you don't have the latest, (NI-VISA 3.2) then you might want to upgrade this driver on the host computer, and then reinstall software on your remote target.
You can download the latest version from:
http://digital.ni.com/softlib.nsf/webcategories/85256410006C055586256BBB002C0E91?opendocument&node=132060_US
(linked here)I hope this helps. Let me know if you're still having problems.
Regards,
Vineet A.