Hi,
As basically already answered by others...
The are two types of error messages in TestComplete.
First type is of 'runtime engine' origin and are caused by the errors like division on zero, missing or incorrect function parameters, attempt to multiply string by two, etc. These errors are handled by the means of the given scripting language (try/catch, try/except, On Error Resume Next). I.e. these are programmatic errors. Errors of the first type are not handled by the OnLogError handler.
Second error type is of 'TestComplete origin'. These errors are triggered when TestComplete cannot interact with the UI object directly referenced in test code. The reason for this may be because the referenced object was not found, or is overlapped by some other (modal) window (this also triggers OnOverlappedWindow or OnUnexpectedWindow event) or control, etc. I.e. these are 'logical', but not programmatic errors. Everything is correct from the scripting language point of view in this case. Errors of the second type can be handled using the OnLogError handler.
