Well, I can make it work but I'm not any clearer on what is causing the problem - it feels like I have to teach CE how to read my rule file by showing it the file in bite sized pieces.
As per my first post - if I start CE and try to export using the whole rule file it takes very very long time (it took ~6hours to export 1 building)
However, if I comment-out 3/4 of the rule, save all and generate models,
then comment-out 1/2, save all and generate models,
then comment-out 1/4, save all and generate models,
then use the whole rule file save all and generate, my model exports in 1.4 seconds. If I do it like this it is very quick to export.
I seem to have to do this commenting-out in at least 3 steps (1/3, 2/3, all) but doing it in quarters seems to be quicker.
I will continue to try and specific problem with my code but at the moment I'm at a bit of a loss. Could it be a caching/memory problem?
...and to answer you questions:
no error entries
exporting to collada
I'm using 25 materials (but I have various case statements that allow for up to 125 different materials)