Internal error 2 in module 5

‘Internal error 2 in module 5’ displayed when a user tried to log into Navision Financials 2.6. I did a search on the forums,but it doesn’t seem to have been reported before. Anyone have any ideas as to what this error means? Any help is much appreciated. - Mike

Navision explanation: These are very much internal errors. Something to do with BinaryTrees. [:D]

My NSC started a journey to update me to Navision 2.6 G with Hotfix 2 then there were no problems anymore