You've read and understood the message correctly (amazing how many people appear to make no attempt to read these message before posting them), however your conclusion is slightly off target.

The problem is actually in the path name being used to try to find the file. The text DIR_WS_TEMPLATES is a PHP constant and should have been expanded to give the root for the path where the file can be found. What we need to investigate is why that constant hasn't been found and used properly.

First place to look is at about line 35 of your includes/configure.php file. Is it defined there, at the end of a block of 8 similar definitions?