Create an action fails "Select an action to add field is required"

I cannot create any action. It always fails with the following message:
"Select an action to add field is required"

The log entry says:

Type form
User admin
Location http://www.controlchainmanagement.org/admin/rules/rules/rules_2/add/acti...
Referrer http://www.controlchainmanagement.org/admin/rules/rules/rules_2/add/acti...
Message Illegal choice in Select an action to add element.
Severity errorWatch

I tried
- 2 types of actions "Send a mail to an arbritrary mail address" and "log to watchdog".
- upgrading to 6.1 to latest dev
- uninstall and reinstalll: this was not possible - unistall does not proceed