When trying to save a new variant, nothing is occurring.  Within the DNN event logs, we see the following.

Any ideas?  We're using the DNN avanced url management.  Thanks..

Url Processing Exception:Exception in Url Rewriting Process
Http Status:500 Internal Server Error
Original Path:http://%websiteURL%/DesktopModules/cartviper/CVAjaxHandler.ashx?alias=%websiteURL%
Raw Url:/DesktopModules/cartviper/CVAjaxHandler.ashx?alias=%websiteURL%
Final Url:null
Rewrite Result:[no rewrite]
Redirect Location:[no redirect]
Action:Continue
Reason:Exception
Portal Id:-1
Tab Id:-1
Http Alias:Null
Debug Message 1:Exception: The URL-encoded form data is not valid.
Debug Message 2:(TRUNCATED TO 500 CHARS): Stack Trace: at System.Web.HttpRequest.FillInFormCollection() at System.Web.HttpRequest.get_Form() at System.Web.HttpRequest.get_Item(String key) at DotNetNuke.Services.ClientCapability.FacebookRequestController.GetFacebookDetailsFromRequest(HttpRequest Request) at DotNetNuke.Services.ClientCapability.ClientCapabilityProvider.GetClientCapability(HttpRequest httpRequest) at DotNetNuke.Services.ClientCapability.ClientCapabilityProvider.get_CurrentClientCapability() at Do
Debug Message 3:Inner Ex : Operation is not valid due to the current state of the object.
Debug Message 4:Stack Trace: at System.Web.HttpValueCollection.ThrowIfMaxHttpCollectionKeysExceeded() at System.Web.HttpValueCollection.FillFromEncodedBytes(Byte[] bytes, Encoding encoding) at System.Web.HttpRequest.FillInFormCollection()
Exception Type:System.Web.HttpException
Message:
The URL-encoded form data is not valid.
Stack Trace:(TRUNCATED TO 500 CHARS): at System.Web.HttpRequest.FillInFormCollection() at System.Web.HttpRequest.get_Form() at System.Web.HttpRequest.get_Item(String key) at DotNetNuke.Services.ClientCapability.FacebookRequestController.GetFacebookDetailsFromRequest(HttpRequest Request) at DotNetNuke.Services.ClientCapability.ClientCapabilityProvider.GetClientCapability(HttpRequest httpRequest) at DotNetNuke.Services.ClientCapability.ClientCapabilityProvider.get_CurrentClientCapability() at DotNetNuke.Enti
Inner Exception Message:Operation is not valid due to the current state of the object.
Inner Exception Stacktrace: at System.Web.HttpValueCollection.ThrowIfMaxHttpCollectionKeysExceeded() at System.Web.HttpValueCollection.FillFromEncodedBytes(Byte[] bytes, Encoding encoding) at System.Web.HttpRequest.FillInFormCollection()