You were right. Disk space was almost unexisting. I removed some old backups and now I have this:
System load: 0.89
Processes: 111
Usage of /: 92.2% of 29.40GB
Memory usage: 83%
Swap usage: 29%
=> / is using 92.2% of 29.40GB
The forum went online almost instantly after that. Thanks!
However, as you can see from the stats above, I’ll probably have the same problem in a while. What can I do to free disk space, apart from reducing the number of stored backups? I once had the download remote images to local feature activated, but not anymore (since a few months, actually). Maybe I could delete something from there?