Won't your connection be good enough to simply use the browser to download?
If not firstly make sure your firewall isn't blocking the downloader.

I suppose you've double-checked your information is right?
If it is, then it is a strange occurrance, given that you could apparently log on to the website without problem, thus it's not with GOG the server not recognizing your login information. You could try sending an e-mail to support inquiring about the problem.

I believe your log on is case sensitive as well.

hm.. yes im 100% sure i entered the information correctly.
I will try again later, anyway im downloading the game with the browser...

If the file is more than 2 gigs, use the downloader. Try it later. I have that problem constantly.

Used the GOG downloader to try and work around a problem in the browser and it worked great. The same thing happened to me though when I first signed up and tried to load a download, it didn't respond to anything I was doing. Then it didn't take my login information either, but eventually after reloading the downloader and signing in again after logging off and shutting down it worked fine for me. Hope it's as easy for you.

Allright.. ill try again later...
Already downloaded the game, Postal 2 ! couldnt find it anywhere !
GOG is great, now i just want max payne on GOG and ill be happy for the rest of my life :]

No file is more than 2 gigs. If a game is more than 2 gigs, the installer is split up into files of 2 gigs or less.

What? . . .No love for Painkiller Black, One Unit Whole Blood, Duke Nukem etc. etc. . . . =)

You know what I meant. =P

No, not really.
I see only two possible reasons to use the downloader, ever. If your connection is highly unstable, or if you don't have unlimited download and need to break the download up into smaller chunks to avoid going over your quota.

I used the downloader because this way i selected where i want my games to be installed.
I also bought bloodrayne, and yeas, i like the painkiller games also, ill buy them soon.

You can do that if you DL with your browser as well. I don't use the downloader at all and DL all my GOG games through my browser. I install them all on my F: drive. Just hit the Options button at the bottom left of the installer (after the verification process) and you can choose where you want it to be installed.

One more use for the downloader: once I had to re-download the installers for virtually all my games because some nasty virus destroyed them (and I had no back-ups yet...). The downloader made it way easier to do.