PDF troubles

Hello,

I usually create PDF's from other apps - namely, ArcMap and Autocad -
and import them in PS to fiddle with them. Now, I never had any
problem doing that with CS, but CS2 is giving me all sorts of
headaches:

- the preview window. I really don't want that. I mean, if I'm
importing a full-page A0 at 150 dpi the rasterizing process is already
long enough without having to wait the additional minutes (minutes!)
for the tiny, useless preview image. I can't seem to find a way to
turn it off, but I trust someone here will point me to the hidden but
obvious solution?

- Every now and then (usually when I'm on a deadline) I get a
perfectly-looking PDF file, except after rasterization it becomes a
blank image. I *can* get an actual working image by exporting as a
TIFF from Acrobat, but that makes it lose transparency - which I
really do need, of course. I tried different resolutions to no avail -
it must be said that it only happens with vectors, but knowing that
doesn't help me much.

Help?

ADP.

P.S: oh yah: P4D 3.2 ghz, 2gb RAM, Xp pro SP2.