Since chrome or chromium for that matter sometime does not seem to handle profiles correctly, I had some trouble making chromium usable again without losing all of my settings. Luckily here are some tips how it might work.
If you are using chromium with ubuntu and you ever had an error message stating that your chromium user profile could not be loaded respectively opened... The german message looks like this:
Ihr Profil konnte nicht ordnungsgemäß geöffnet werden. Möglicherweise stehen nicht alle Funktionen zur Verfügung. Überprüfen Sie, ob das Profil vorhanden ist und Sie Lese- und Schreibzugriff für die Profilinhalte besitzen.
The english message should look like this:
Your profile could not be opened correctly. ....
You might wonder (like I did) and try some cache invalidation and so on. It didn't help...
And checking the write and read access didn't help either.
Chromium Profile Fix
I tried a few things...
What I thought would work
go to '~/.config/chromium/YourProfile and delete all caches from subdirectories like Application Cache/Cache or Storage/ext/chrome-signin/def/Cache/.
What helped (so far)
removing (backup before removing) the whole ~/.config/chromium/ directory and let chromium (after restart) create the new settings. WARNING: if you do not use your google account to sync your settings and so on you will have to install and configure it manually, again.
What could help
Delete (or rename) the file ~/.config/chromium/Default/History.