Raster Images Won't Display

I'm hoping this is a no-brainer for someone....In the past, I've inserted
Images into drawings and had no problem scaling them, turning frames on/off,
understanding transparency, etc...and they would display in their entirety
even when not selected. Suddenly, I'm finding that once I insert an image,
it disappears from sight. If I drag a window to select where I know it to
be, it displays (with or without a grid depending on its transparency
setting), but when unselected it goes away again. I have traced images in
the past, but now cant initiate a line command w/out the raster image giving
me the slip...I've tried display order, ensured all layers (including
current) are unfrozen and on, detached and re-attached the image, tried a
variety of different images of various formats (gif, jpg, etc.), and checked
/unchecked any & all options I can find under options which might affect
it's display or behavior. Help!!