I have the same thing after upgrading to DNN 6.2.3. - my test site works great but my live site is throwing this exception everywhere:

Server Error in '/' Application.

Sequence contains more than one matching element

Description: An unhandled exception occurred during the execution of the current web request. Please review the stack trace for more information about the error and where it originated in the code.

Exception Details: System.InvalidOperationException: Sequence contains more than one matching element

Source Error:

An unhandled exception was generated during the execution of the current web request. Information regarding the origin and location of the exception can be identified using the exception stack trace below.

Stack Trace:


[InvalidOperationException: Sequence contains more than one matching element]
System.Linq.Enumerable.SingleOrDefault(IEnumerable`1 source, Func`2 predicate) +2715502
DotNetNuke.HttpModules.Membership.MembershipModule.AuthenticateRequest(HttpContextBase context, Boolean allowUnknownExtensinons) +721
DotNetNuke.HttpModules.Membership.MembershipModule.OnAuthenticateRequest(Object sender, EventArgs e) +81
System.Web.SyncEventExecutionStep.System.Web.HttpApplication.IExecutionStep.Execute() +148
System.Web.HttpApplication.ExecuteStep(IExecutionStep step, Boolean& completedSynchronously) +75

---

Entrepreneur

PokerDIY Tournament Manager - PokerDIY Tournament Manager<
PokerDIY Game Finder - Mobile Apps powered by DNN
PokerDIY - Connecting Poker Players

Note: My site suddenly went down again with this issue (and an IISReset fixed it). Is anyone else experiencing this on DNN 6.2.3? It could be more serious than I thought originally..

---

Entrepreneur

PokerDIY Tournament Manager - PokerDIY Tournament Manager<
PokerDIY Game Finder - Mobile Apps powered by DNN
PokerDIY - Connecting Poker Players