Non-existent error 3001

TB 6 Silver sometimes he follwing error message:
Division by zero [3001]
Occurred at 55 in Indata in Main program
Called from 155 in Main program

This error message cannot be removed. I have deleted both the offending rows but the same message stills pops up. I did have a division by zero in a different position and removed that by deleting an entirely other row. The error message just jumped to another line without any text in it:

Dision by zero [3001]
Occurred at 204 in the main program

I tried to save the code as a .txt-file and changing the suffix to tru, but that did not help. The same error persisted. Deleting all text on the offending lines does not help, either. WIndows 7 Professional, English.

Anybody who has solution? This quirk destroyed a 1500 line program!

Another problem: Why have you removed the option of activating text by clicking at both ends of the selection? Copying by dragging the cursor is now the only way of doing it and that takes ages.