Your code runs as expected wo error .

If you debug at this moment is the alias used?

Some timer kicking in...

Any change on this?

IF !FILE(xlngfile)
 IF USED("language")
  SELECT LANGUAGE
  USE
 ENDIF

 RETURN nesne
ENDIF

IF USED("language")
 SELECT LANGUAGE
 USE
ENDIF
SELECT 0
USE (xlngfile) ALIAS LANGUAGE AGAIN SHARED &&----error occurs at this line

Or ist just your strange inline comment? :)
>Hi All,
>
>This's very strange for me. Occurs sometimes at customers, never happened me or our testers. Just a simple code:
>

>If Used("language")
>	Select Language
>	Use
>Endif
>
>If !File(xlngfile)
>	Return nesne
>Endif
>
>Select 0
>Use (xlngfile) Alias Language Again Shared //----error occurs at this line
>

>this line gives "Alias name is already in use" error. But I close table at the second line. How can this error occurs?