Apex Session state protection violation

You can get the following verbose error message in Oracle Application Express (Apex) 3.0.0.00.20 when you try to open the "Create" script page from the dynamic menu tree of SQL Workshop:

Session state protection violation:
This may be caused by manual alteration of a URL containing a checksum
or by using a link with an incorrect or missing checksum.
If you are unsure what caused this error, please contact
the application administrator for assistance.

The workaround is to click on the big icon of SQL Scripts and open the "Create" page from there.

Oddly enough this problem seems to affect only sessions started with the English language, because i didn't get any error when i tried to do the same with the browser's language set to "es-mx" or "it".