I just realized that when I try to modify a table after a default value has been introduced, following changes are just ignored. They appear in the modify table window and the "query" on the bottom is updated, but if you hit OK, nothing else happens. I also realized that you usually get a little window after any change that dissapears very fast (I think that it reads "executing SQL" or something like that) but once you introduce a default value, that window doesn't appear anymore.

If you remove that default value, everything is working fine

I also realized that if you open the modify table again after setting a default value, it now appears as 'value' instead of just value (I mean, quoted)

Here you can see an example

I am running Win8.1 64bit, SQLite Database Browser 3.2.0 and I have these additional versions on the About... window: Qt Version 4.8.5 and SQLite Version 3.8.4.3