Q: Why does Ride7 emit "Script error in line xxx" messages in its build window ?
To reproduce the problem, you can open a project an press the "Project | Clean" menu, which triggers the problem.

A: Restore the COMSPEC environment variable to its default value (for example "ComSpec=C:\Windows\system32\cmd.exe").

The problem is caused by the absence of the COMSPEC environment variable, which is used by Windows.
If you have removed this environment variable, then Ride is not able to run command scripts anymore and the message is displayed.