Ciao guys,
short update after having tried all suggestion above (except remove DEM data from my basemap). The only sensible difference thanks to the format of the internal memory is that now my Garmin takes approx 10 secs to get connected to the pc while in the past I had to wait more than 30 or so.
Apart the above, the drawing problem is still there and nothing helped (clearing NV, format internal memory, auto rebuild of the file structure, defrag, download of maps using mapinstall,...).
I've now just removed the basemap in full and I'm gonna give the last try tomorrow morning. Will let u know by return. In case you have any other idea... :-)
Tks a lot.