looks like a rails issue, since we 'solved' #640 with [722].

We really need to go to rails2.0 after releasing 1.5

I don't think this has anything to do with rails versions. The migration is setting the default value of an integer column to false. That may fall through the cracks on some of the lesser databases, but that doesn't make it correct!

change_column :projects, :position, :integer, {:null => true, :default => false}
change_column :contexts, :position, :integer, {:null => true, :default => false}

that doesn't mean "don't have a default" it means the default is false!

ok, so this is semantics. I thought that you can remove the default value of a column when using change_column with :default => false. If this is not the case, what is the right construct to remove default value?

The default default value is NULL, so setting :default => nil would do the trick

From the postgres docs:
"If no default value is declared explicitly, the default value is the null value. This usually makes sense because a null value can be considered to represent unknown data."

I've changed migration 038 to use nil instead of false. See [748]. It works on my mysql setup. I do not have postgreSQL to test. Please reopen if this does not solve it.