Thanks for the help Pepper.
I only just found the site that that was taken from today (followed a link from seventh's compiler-reading post). Wish I'd have seen that sooner - that would have solved at least half the problems I've been having lately!
Just out of interest, when trying to fix the problem last night I was looking at this line in the defenition you gave above...
"message is simply alerting you to the fact that one of these winding data structures has a larger number of points than expected, and one of the points was ignored".
Now, this might be a bit of a noob question - but looking at each individual brush in my map, there are none that have a particularly 'large number of points'. There's no complicated geometary in there, or any crazy vertex manipulated brushes. The whole thing is constructed out of very simple shapes (triangles and squares basically). In the case of the arch I described above, it's constructed out of about 80 narrow triangles in a fan like arrangement. To make working on the map easier, I grouped them all - so does that mean that the compiler sees all the grouped brushes as one brush with loads of points, or does it see the grouped traingles as just that - a whole bunch of individual triangles?
Also, sorry to be a pain, but when constructing complex architecture, rather than using vertex manipulation, I prefer to painfully construct things using loads of little triangles - as it helps give a more organic feel to the spaces and I have more control over the shapes I end up with. Is this a good practice? Or am I just over-complicating things for myself?
Once again, thanks for the advice guys...