VBA AdfinX Real Time Error Message ERROR #360f

I'm using VBA and the COM API to retrieve closing prices (CL_CLOSE). Here is a code snippet:

With myRTList    
  .ErrorMode = DialogBox  
  .Source = "IDN"    
  .RegisterItems ricString, "CF_CLOSE"   
  .StartUpdates RT_MODE_ONUPDATE  
End With

The variable ricString is a string with many instrument RICs (e.g "DBKGn.DE,BMWG.DE,BMWG_p.DE")

It works fine until I have more than 244 RICs in the string. In that case I receive an error "#360f AdxRtList:invalid item". Though my RICs in the string are okay..

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AdfinX Real Time Error Message

ERROR #360f - AdxRtList : invalid item

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I would appreciate some help.