glimmer games downloads downloadMy computer won't download anything. What could be wrong?

I will try to give as much detail here as possible.
It appears as if the item is downloading. It shows the little bar and % left of the download. I have even right clicked to open the containing folder and the file will be there, on my desktop (downloads folder, etc.) then it just DISAPPEARS! Then I go back to my downloads list on my browser and try to open it from there and the options are gray to open or to open containing folder and you can't do anything with it. Its like it never was there.
I have Windows Vista. I am running Firefox, but I have also tried to download from Safari and IE as well to see if it was a problem with Firefox, and nothing would download from there either. I have tried muglimmer games downloads downloadltiple types of files from different websites. I have disabled all firewalls. I have scanned for viruses. I have cleaned my registry with CCleaner. I did a system restore to a date before I had this issue. Nothing thus far has worked. However, I downloaded an online game which used its own downloader program which I had installed from a much earlier date when I didn't have this problem.. So that was my glimmering light of hope!!
I have googled to death looking for websites to help me. I have found people with sooorrrtt of my issue but not quite.. So I come to you, trusted Yahoo! Answers friends.
Any ideas on how I can solve this issue? Has anyone had this problem before?
Kia have you tried to openglimmer games downloads download your control panel and go into remove programs make sure that whatever your trying to download hasn't been partially installed which would prevent it from downloading again. Also i guess your firewalls could prevent a download also if the item your downloading is potentially dangerous to your system. Either way i hope you get it figured out...if not call me and ill call my brother who has a degree for this crap and see what he says. TTYL. Samantha
An error in the download or the site disconnecting before the download complete will delete the partial downloaded item. Try getting a download manager program that can re-start interrupted downloads and you may solve your problem.