I followed Wes' great GL preview window example from this thread:
in a patch I'd built six months ago for a live performance. Worked like a charm. I haven't changed anything in the patch, but I've since switched machines from a Powerbook G4 12" (Geforce FX5200Go) to a first-gen MacbookPro (Radeon x1600).
The problem is that the preview pwindow just shows white. I'm not getting any errors.
Wes' example still works fine, but in comparing my performance patch to the example, I can't seem to find what is going wrong on my patch, since I built it straight from the example. I've posted below a patch which just has the gl objects as they are (and named) in my performance patch, and substituted the source material with a dummy shape. The only thing to do is switch on the two checkboxes to render the main mix window and the "preview" pwindow.
Maybe I'm just blind and am missing something very obvious!