>Are you guys stupid or what?
>
>I said: 'The error above was catched with an error handler' so I'me already cathing errors to a text file!!!
>
>And I tested my application of course first without COM!! So why do I catch this error:
>
>>Error:2031
>>Error message: User-interface operation not allowed at this time.
>>Line of code with error: 600
>>Line number of error: 9
>>Program with error: DOS.SELECTIONEXISTS
>>
>>In this line:
>>
>>USE (THIS.SelDir + '\S_Seldef') IN 0 AGAIN ALIAS SelectionExists_Tmp
>
>and not an error like 'File not found'

You are not listening. You still didn't tell us what the exact text you have as a result of (THIS.SelDir + '\S_Seldef') expression. Check it with the FILE() function first.
There is only one reason for "User-interface operation not allowed at this time" message - VFP is trying to pop up a dialog window. Obviously it cannot find the file you are trying to USE. That's up to you to find out where exactly it is trying to look for it and has you provided the valid name and path accessible from where your COM starts.