bug in 1.6.1 display png image

[asm23]

hi all:
it seems in 1.6.1 , in windows, the png image was not converting 
properly and can't be displayed. I close lyx and reopen it, but the 
problem still exist. I suspect I have the long folder name, but I 
eliminated this case.

see the attachment of the screen shot.

But the jpg image were displayed properly. I'm sure the path of 
ImageMagick was right.

Any suggestions? Thank you!
<<inline: Snap1.jpg>>