Graphic causing Frame to crash

[Lin Sims]

FrameMaker 8
Windows XP SP3

I have a a couple of .png graphics that I copied to a Master Page.
Every time I use the right-click menu to select Object Properties,
Frame crashes. I tried converting the graphics to GIF but got the same
result.

These same graphics will, sometimes but not reproducibly always (at
least not that I've noticed), disappear, leaving a grey box behind. So
far that's been fixable by reimporting the page layout from elsewhere,
but I'd rather not have to worry about that happening.

Does anyone know what might be causing this and, more importantly, how
to fix it permanently instead of with a bandaid?

Thanks.

-- 
Lin Sims