I've been having the same issue. Also using 2.5.1.17. Will try the beta (hopefully tonight).
The hang is frequent (about half the time for me). One thing I've noticed is that if I can cancel and then immediately re-initiate the solve and it will fly through no problem. When it "hangs" (PlateSolve2 window does not come up), it will say "Image preview opened ..." in the main window status bar (lower left).
Dave