So, I've become aware of this problem again this morning by loading two different Workspaces (different instances.)
The one I'm working on includes a Code Files list of basic files, but the Workspace is loaded with more files than that on Tabs. The last file in the Workspace Tab area is an INCLUDE file (.basinc).
My reference Workspace has a mix of basic and INCLUDE files in the Code Files list. The last file on the Tab area is a basic file (.bas).
The first Workspace above has a greyed-out "Check Syntax" button on the Home tab, but a working one on both the Simulate and PICAXE tabs.
The reference Workspace has a working "Check Syntax" button on all three tabs.
...
Can it be that the difference between greyed-out and working is that the INCLUDE file is loaded in the last Workspace tab?
PS. PE 6.0.9.3 (Windows 7) (and previous versions)