try the contrast setting make sure its at 50
(in the same panel u might see brightness)

what colorspace are you using for your assets in cs4? rgb or YV12?

Where could I find those settings at?

colorspace would be chosen when you convert your footage.

example, rip a dvd to vob the colorspace is YV12. this vob should be pre-processed with ivtc (if necessary), deinterlace (if necessary) and the colorspace converted to rgb (this is the colorspace that AE and premiere works in). when you finish editing you export uncompressed avi, then when you convert to your final destination (i.e. mp4, you convert the colorspace back to YV12).

other options to check are your:
color depth (alt-click project settings button i.e. 8 bpc)
plugins may be affecting the output (i..e color correction)
bad footage

also some general rules of thumb:
1) use the highest quality footage available (compressed video files are a no no)
2) ivtc, deinterlace and convert to RGB before importing footage
2) make your comp the same ar, par and res as your footage. if using footage of various res, resize your footage to desired output (i.e. 640x480) or use the res of the largest
3) always output from after effects to lossless uncompressed avi. there are way better converters outhere (virtual dub, mequi, quicktime, etc)

Thanks! I figured out how to deinterlace at the encoding level on Premier and at the conversion level on MPEGStreamclip. So my lines are gone now. But, some of my videos still come out dark. Not all, just some. :(

What is your source footage (Promo only DVD, other)?

One is a VOB from a Promo Only UK video and the other 2 are FLV's a friend sent me. They look fine on Premiere, it's just when you render that they come out dark.

I convert all my source files to ProRes 422 using MPEG Streamclip than when I'm done editing I render them to H264 straight from Premier. Even if I render them to MPEG and then convert them to MP4 using Visual Hub, they still come out dark.

I'll take screenshot of my settings and process in a bit.

THAT IS HAPPENING TO ME TOO i am using premier a long time ago and i never see that befoure, i have premier cs4 with the upgrades
and every time i do rendering with premier look much dark that it is
some one know more about the problem ?

i am using cineform HD

Hi - I believe the problem is when you make an export at a different frame rate from your original source file. I had this same problem - my source material was at 29.97fps - I inadvertantly exported (QT H264) at 25 fps and the export was dark. I tried an export at 30fps and it was also dark - When I exported at the same fps rate as the source file 29.97, the export was perfect.