To reproduce this issue:
1) Add new portlet "Web Form"
2) Configure it
3) Go on Tab "Form Fields"
4) Add a new field and enter a long text as name (text must be longer than 75 characters)
5) Save and go back (make sure that option "Save Form in database" is checked)
6) Fill the form and press the submit button
7) An error message appears on the screen. In the log file, you will see something similar to:
18:26:26,541 ERROR [WebFormPortlet:331] The web form data could not be saved to the database
com.liferay.portlet.expando.NoSuchColumnException: No ExpandoColumn exists with the key