Now I have the same issue with PA A320
Another free A320 ? I guess both are using the same set of gauges, which obviously is the only part of an airplane that could create such problem.
( Whats wrong with that planes?
This was already explained: there are a couple of A320 around (but now I really think the culprit is just a single gauge) that, for unknown reasons, write their own stuff into the reserved memory area for sceneries, something that doesn't make any sense to do, considering a C gauge has the whole PC memory for use.
It looks like if there is something wrong with the demo mode 
No. The demo mode works absolutely fine. The problem is that airplane gauge. I wonder how airplane designers would react if we started to write funny stuff into THEIR memory area...we'll probably get the blame (and with good reasons) immediately.