I have read some other posts about people having trouble with portal settings not saving when changed (http://www.dnnsoftware.com/answers/duplicates-keys-in-sitesettings-portalsettings) but there seems to be a range of different suggestions as to what causes this including the culture setting for the portal. We have looked at those fixes as well as trying setting the default language back to en-US and disabling any other languages and even after upgrading to v7.3.3 the issue still exists across several different installations and portals using different skins.

There is no error given when saving the page and the only indication of a problem is the entry in the event viewer log which includes:

RawURL:/Admin/Site-Settings

InnerException:An item with the same key has already been added.

Method:System.Collections.Generic.Dictionary`2.Insert

Message:
System.ArgumentException: An item with the same key has already been added.
at System.Collections.Generic.Dictionary`2.Insert(TKey key, TValue value, Boolean add)
at DotNetNuke.Entities.Portals.PortalController.GetPortalSettingsDictionaryCallback(CacheItemArgs cacheItemArgs)

Has anyone found a work-around for this because we have a portal that needs to allow public registrations but without the ability to set a valid profile as required and/or the captcha as required for registration we are not game to try it given the host of sites being targeted with spam registrations.