Hi Martial,
This is a new feature of VI, it loads Presets that were saved with disabled cells without loading samples (the cells are pale blue). The only VI Presets that are affected are the Synchron Strings Presets.
You have more options to load those cells in the SETTINGS menu - to the left of the BASIC/ADVANCED View buttons. My suggestion is to activate "Enable cells on MIDI Activity", which will load the needed samples in the background whenever you play a note.
If you right-click on a matrix (in the matrix list to the left), you can "enable" the whole matrix.
In "Settings" (the icon left to the Basic/Advanved View), you can also enable the whole instance and find additional options (like "Force Enabled Cells").
More tips and tricks for Synchron Strings can be found in the SETUP GUIDE pdf and the SETUP GUIDE video!
Best,
Paul