I have the same problem. it has happened several times but typically not every time..
i select save as.. and the explorer appears. as soon as i select any part of the explorer window i see that the application is frozen and not responding.
explorer defaults to my desktop where there are no videos or other pictures. i cant get to the point of selecting another folder instead of desktop.
this is incredibly frustrating since it crashes once my picture is done, then crashes so i have to do the whole thing over again.
like another user said, if save as works once during a session then it will keep working as best i can see. for this reason i now save as soon as i open PDN, thereby ensuring that it will save and not crash later. unfortunately i don't always remember to do this.