Readded to the downloader. Since it will try to download in the same place, it should first check to see what files are already there, then re-check them, and download any that are missing. Alternatively, run the game's setup file, if the setup passes integrity check, your installer is fine.

I skipped the second integrity check to get it to download. Think I need the 3-bin file.something. Will try to download the third section without gog downloader later and see if it will merge right. Game works in the begining ok except for frame skipping. Need better video card maybe.

Now this is new...

For some reason my Opera refuses to use the downloader to open the links.

It will ask me if I want to launch the application to open the downloader link, but when I click "Yes" Opera gives me the error message "There is no associated extension for this operation" or something along those lines.

I am not sure what is going on now...

Opera 12 had (and maybe still has) some troubles with the gogdownloader. Take a look at post 435 and post 439 and see if those help.
Hope you get it fixed soon.

Excellent!
Post 435 helped in the problem, works fine now (manually adding the protocol).

Thank you so very much. Here, have some rep. :)

Can't seem to download anything at all with the Downloader.

I click what I want to download and nothing happens.

Do you have the downloader installed? Do you click on "Game Installer" or "Combined bonus content pack" to add it to the downloader's queue? Are you by any chance using Opera 12, which need to have the gogdownloader protocol manually installed (see a few posts back, or post #435)? Does it happen with all games or a specific one?

Yes, it's installed.
Either or.
Using Firefox.
All games.

Take a look here. Also, are you using the correct downloader version (stable/beta)?

Using the version that was just released but even before that it wasn't working for me.

I don't seem to see it in the Firefox Application list either.

You can try adding it yourself, take a look at post 435 and post 439 and see if these help, even though they are for Opera (but I hope firefox is using a similar system). Also, if you are using 3.0.51b (Stable) make sure this is set to off.
If neither of these help, than unfortunately I'm out of ideas, so you'll have to wait for Fallen_Zen to take a look and solve it, but it is midnight (or near that) at Poland atm, so it will take some time.

Unfortunately, I don't believe that Firefox uses the same framework as Opera but thanks for trying anyways.

Ok, final attempt.
Type gogdownloader:// in the address bar, and Firefox should ask you what program to open the link with. Browse to the GOG.com downloader (if it's not already selected) and tick the "Remember my choice". At least this worked for me with Firefox 13.0.1 so hopefully this should end your worries.

Okay, we're getting somewhere.

That re-added the downloader to my list of applications and it opened the downloader itself.
But, I just tried it again on a game from my list and no luck!

Gah.

Ok, manual linking again to see.
gogdownloader://worlds_of_ultima_the_savage_empire
The above is for The Savage Empire, which you should have already (free and excellent game). Paste it in the address bar and see whether it's parsed correctly.
gogdownloader://worlds_of_ultima_the_savage_empire/1952
gogdownloader://worlds_of_ultima_the_savage_empire/1942
gogdownloader://worlds_of_ultima_the_savage_empire/1972
gogdownloader://worlds_of_ultima_the_savage_empire/1932
gogdownloader://worlds_of_ultima_the_savage_empire/1962
These are also the bonus items one by one, so if the game does work, check with these as well.
P.S. Are you using any addons/extensions that may interfere with link parsing?