My I mac os 10.6.8 screen turns into black when downloading

My I mac os 10.6.8 screen turns into black when downloading applications, y tube won't play the movie, urgent help would be much appreciated THX

1. Which iMac? Find the information in About This Mac under the Apple icon upper left corner.
2. Does the screen go black immediately when you start the download, or does it take a couple of minutes?
3. Did this just start happening recently? Have you installed/changed anything just before this behavior started?

Many thanks Jake,
1. Which iMac? iMac OSX 10.6.8 Snow Leopard
Model Identifier: iMac11,3
Processor Name: Intel Core i5
Processor Speed: 2.8 GHz
Number Of Processors: 1
Total Number Of Cores: 4
L2 Cache (per core): 256 KB
L3 Cache: 8 MB
Memory: 4 GB
Processor Interconnect Speed: 4.8 GT/s
2. the screen went black immediately when I start the downloading/installing, it returns to normal once I got off the download page. Downloading can not be found by using Spotlight.
3. Yes, this just start happening 3 days ago? I checked if all softwares are updated just before this behavior started, didn't change anything at all.

Your attention and help are deeply appreciated.
J4655

How are you starting the download/installation? What steps are you following? Can I ask what you are downloading?

I was trying to download some free compressing applications for Mac, from NCH site, Win Zip 3.0 for mac etc, found the sites and click on the download table, then the screen turns into black immediately. As for y tube, it seems only swf file can be viewed, others just a black placeholder, this has been happening for about 10 months. (While I used the right click to compress the files, it produced a zip file without any compressing at all, the size of fill didn't change at all. that's why I am trying to download a compressing application.) Many THanks for your help. jane

I just went here, but I didn't see WinZip. I did see a zipping file, which downloaded just fine here into a self-extracting file. Is that the site you are using? I can't see any reason for it to go black.

As for not finding your download in Spotlight, it should end up in the Downloads folder unless you've changed the default location in Preferences.

For videos, do you have Flash installed? A lot of videos are in Flash format, so they won't play unless you have it installed. Flash is pretty much of a resource hog, so I don't have it, personally.

EDIT: and which browser are you using?

Many thanks for your help,Jack.

I have just tried to download again the ZIP Express (from NCH site) and checked the download default folder, it still no trace of dmg which should exist. I also have flash installed but y tube is still not working. I always use Google chrome for browning. I will follow your advices and try it again tomorrow, otherwise, I might have to call a technician to repair my Imac. My hearty thanks for your help. Good night!! Jane

It was not a .dmg. It was a .zip file that when clicked, extracted itself. By "y tube" do you mean YouTube? I'm using Safari, I don't use any Google products. Have you tried the download from Safari?