We have two customers who have reported this issue in the past 2 days, and I fear there are more to come.

When they have "Data.com Clean" enabled, doing a simple Contact creation from one of our Visualforce pages (with custom controller) fails with the following error:

Visualforce Page: /apex/i__aaPendingAddrs

caused by: System.DmlException: Insert failed. First exception on row 0; first error: UNKNOWN_EXCEPTION, INVALID_TYPE: sObject type 'DataDotComEntitySetting' is not supported.: []

Class.i.CtlPendingAddrs.insertC: line 228, column 1
Class.i.CtlPendingAddrs.doSave: line 190, column 1
Class.i.CtlPendingAddrs.saveActions: line 162, column 1

The code where the failure occurs is bog standard, simple Contact creation.  This code works perfectly in thousands of installs of our managed package.  Our code does not reference "DataDotComEntitySetting" in anyway.  Here's the code that the stack trace leads to:

  private static void insertC(PagerPending.Item[] items) {
    Contact[] objs = new Contact[0];
    for (PagerPending.Item i : items) {
      if (i.action == 'nc') {
        if (i.addr.LastName__c == null) { i.error = NOLASTNAME; continue; }
        i.newcontact.Email = i.addr.FullAddr__c;
        i.newcontact.FirstName = i.addr.FirstName__c;
        i.newcontact.LastName = i.addr.LastName__c;      
        if (SFDC.hasRecTypes() && i.getCRecordType() != null) i.newcontact.put('RecordTypeId', i.getCRecordType());
        objs.add(i.newcontact);
        }
      }
    if (objs.size() > 0) insert objs;  // THIS IS LINE 228 PER THE
    }

As you can tell it is pretty darn simple.

The error message - with its reference to "DataDotComEntitySetting", which does not exist in our code - shows that this is an internal salesforce/data.com bug.  Our customers who have encountered this issue note that it reproduces with 100% certainty if Data.com Clean is enabled, and disappears when Data.com Clean is disabled.

I'm guessing that Data.com Clean has a trigger on Contact creation that is buggy and throws an error, but somehow the call stack is lost and it, instead, unwinds to the contact insert statement itself.  However, our customers report that contact creation from within the normal Salesforce user interface still works, so it's some complicated interaction between Data.com Clean and managed packages.

Salesforce support - I have opened case 09191025 to track this issue.