I installed Lotus Designer v12 and when I try to open a database with HCL Domino designer I get the next error: "Access restriction: The constructor 'UISelect2PickerCombo()' is not API (restriction on required library 'C:\Program Files (x86)\HCL\Notes\Data\workspace\applications\eclipse\plugins\org.openntf.xsp.bootstrap_1.0.0.201407020945.jar') CcCabecera.java /dddbbbb.nsf/Local/xsp line 251 Java Problem".
It works fine in Domino designer v9.
I tried to change the JDK Compiler Compliance level to 1.5 , add in Target Platform, the folder but always I get the same error
Any help??

You can ignore the error. Go to Domino Designer preferences and change the error to 'ignore'. It's one of the 'api' problems.