Hi Francis
There was a defect found in v1.08 which, according to the probe release notes, was fixed in v1.31. I would assume that you are seeing the issue in the latest version (1.35) GA since 08/10/2013. A possibility could be the probe is obsolete although I couldn't find it in the end-support-list but it wasn't updated for 3 years.
As always, in order to troubleshoot this we need to have a deeper look into the probe cfg and log, plus the nas.log.
Let us know if you need any help with this.
iulian