outside free 3d view limited

hi,I have a fresh flawless FSX install with all addons listed belowin outside 3d views (locked, spot), it happens that panning with spacebar and mouse yields view constraints: I cannot go up more than about 20 degrees in the upper hemisphere, and laterally I have limitations from about 20 degrees (bearing from the aircraft) to 180 (I hope to have explained well the issue :) )worst than ever, it happens about in 50% times and with the same FSX configuration, so I cannot figure out what to try to resolve this weird problemthanks for any "intuition"BTW maybe it happened in the past years and I don't remember the solution :(