Does anybody know what this message mean:

"Index was out of range. Must be non-negative and less than the size of the collection. Parameter name: index"

I never use a paameter "index" in my espace.....
The Service Center Log displays the following error (stack):

at System.Collections.ArrayList.get_Item(Int32 index)
at OutSystems.Nssods.Latin1ToGSM.GetCorrectMessageSize(Byte[] message)
at OutSystems.Nssods.Cssods.MssCalculateSMSSize(String ssMessage, Int32& ssSize)
at ssSMSServiceManager.Actions.ssServiceCapture_UpdateContent(HeContext heContext, Int32 ssOrder, RCServiceContentRecord ssContent, Int32& ssOutOrder, String& ssOutMessage)
at ssSMSServiceManager.Actions.ssServiceCapture_FragmentContent(HeContext heContext, RCServiceContentRecord ssContent, Int32& ssOrder)
at ssSMSServiceManager.Actions.ssServiceCapture(HeContext heContext, Int32 ssMenuEntryId)
The message is an c# exception that was raised by an extension method call and no error treatment (try/catch) wraps that call.
It means that the value of an argument is outside the allowable range of values as defined by the invoked method.
"index" is the parameter name of system method "System.Collections.ArrayList.get_Item(Int32 index)" as you can see in the error stack.

For further information about this issue, please check the following references at Microsoft:
ArrayList.Item Property

For Information about handling External exceptions in Service Studio see:
Service Studio Help\Managing exceptions\Types of exceptions\External exceptions