For those having the problem of the downloader staying mimimized all the time, I got mine working again. The problem seems to be with Adobe Air. Here is what I did. I don't know how long it will stay fixed but it's working again for now.
1. Uninstall GOG Downloader and Adobe Air.
2. Delete all remaining Adobe Air directories.
3. Use regedit to delete all entries with AdobeAir and Adobe Air. (WARNING: If you're not familiar with using regedit then maybe you should not even try this.)
4. Restart computer and reinstall Adobe Air and GOG Downloader in that order.
You should now be able to maximize downloader. Might not be a big deal to most of you but my ISP limits my daily bandwidth and I have to schedule downloading at night and be able to resume downloads.
Good luck. Hope this helps some of you.