Database opens in "Read Only" mode

Regularly, when I open a database in Base, it opens in "Read Only" mode (my
terminology because it really doesn't say so on the screen).

What happens in this case that all the links in the left top pane of any
Base screen, i.e. Tables, Queries, Forms, etc. are "greyed out". I can see
the tables and when I click on a table name it dumps its content to the
screen, but all links are dead, so I can't create queries, edit tables or
whatever.

Sometimes after a while it goes away and the database opens properly and all
features can be used. Sometimes it takes just too long and the only
"work-around" I have found is to delete and recreate the database (they are
MySQL databases linked to Base via JDBC). Which is fine at the moment
because I am experimenting, but would not be acceptable when I go into
production mode.

So far I have found no logic for what causes this.

Help please.

TIA
Gert