Everything has been working well until today I started experimenting with PiP. I have the main project on Track 2 and the clip to be inserted on Track 3. When I drag a PiP effect over the clip on Track 3 nothing seems to happen except that the description of the effect shows up for a short time over Track 3. However, the effect does not appear when I play the tracks. But now neither the left click nor right click mouse buttons will work in PRE12, not even on the icon in the task bar (they worked very well before); the mouse wheel still moves the timeline left and right but I can not longer "grab" the CTI with my left click arrow. The mouse buttons work well everywhere else (including PSE12 which I opened with PRE12 open just to test) while the non-responsive PRE12 was still on my desktop. Because the mouse buttons don't work I have to use the Task Manager to shut PRE12 down. There is no problem in starting it up again in the same project and the mouse buttons work as intended. But as soon as I try to apply a PiP effect the mouse buttons stop working as described above.
Any ideas as to what is going on here?
Many thanks.