When I tried to run a GLUT/GLUI program in 10.2.4, which ran perfectly in 10.2.1, I got an error saying:

2003-04-04 00:59:41.524 glui[1804] _NXCreateWindow: error creating window (1002)
2003-04-04 00:59:41.551 glui[1804] _initWithWindowNumber: error creating graphics ctxt object for ctxt:0, window:-1
2003-04-04 00:59:41.609 glui[1804] *** Assertion failure in -[GLUTView lockFocus], AppKit.subproj/NSView.m:2343
2003-04-04 00:59:41.630 glui[1804] GLUT Fatal Error: internal error: NSInternalInconsistencyException, reason: lockFocus sent to a view whose window is deferred and does not yet have a corresponding platform window

Is this a GLUT or a GLUI problem?

Could be GLUT, have you tried grabbing Apple's source, building and trying it?