When you click on the unsubscribe link in an email, you get an error message:
The following error(s) must be corrected before continuing: Date could not be saved. The INSERT Statement conflicted with the FOREIGN KEY constraint "FK_CONSTITUENTSOLICITCODE_CONSTITUENTID". The conflict occured in database "40731-389dd6f7-83e8-aefc-ab27-d8ce3cbb6e2b", table "dbo.CONSTITUENT", column 'ID'.
Download and install the latest patch, which contains all fixes from previous patches. If you are running an older version, download and install the latest version and then the patch.