lazydog: I had this problem not too long ago, when I contacted support this was the first thing they suggested and it worked:
please redownload and reinstall the Downloader:
https://secure.gog.com/downloader I have the rest of the possible steps if this doesn't work.
Hope it helps you.
jellysgirlfriend: Unfortunately it didn't work... Would be grateful for other possible steps
Here is the full email response I got with all steps (I should have just posted it all last time!)
First, please redownload and reinstall the Downloader:
https://secure.gog.com/downloader If that doesn't help, delete the contents of your user account's GOG.com folder - its location depends on your operating system:
Windows Vista/7: C:\Users\USERNAME\AppData\Local\GOG.com\
Windows XP: C:\Documents and Settings\USERNAME\Local Settings\Application Data\GOG.com\
Then try launching the Downloader.
If that doesn't help as well, you should verify that your .NET installation isn't corrupted. To do this, use the .NET Framerowk Setup Verification Tool and choose .NET 3.5 SP1:
http://blogs.msdn.com/b/astebner/archive/2008/10/13/8999004.aspx Please also make sure that the Downloader is registered with your browser:
http://www.gog.com/support/support_view/registering_the_gog_downloader_in_common_browsers If that doesn't help, you could contact support but it might take a couple of days.