Sorry if this is too elementary a problem to be discussed here - I'd happily take a reply by PM!
No, it's better to have it here. More people will be able to help you, and others people who have the same problems in the future may find it.
If you can't build an existing firmware with a clean checkout from SVN, then something is wrong with your build environment. I'd suggest working that out before you worry about getting new code working.
Well - I really hope you've got the patience to see me through this, and that it will help someone else - I promise I will limit myself to a single daily update.
Today I began trying to sort out the build environment, concentrating first on trying to compile SD950 v100d.
I deleted CHDK shell for Windows 2.70 and all associated files and reinstalled it
I allowed it to load trunk 885
I put the 100d primary.bin in sub>100d
I compiled (all compilations using the command line and the clean fir command) - it worked.
I then added the six reference files to the tools folder one by one, compiling each time. The compilations worked until the last one (dryos_3). Then I got the ExitFromCompensationEVF error message. I could then only compile after making the file alterations detailed in my post above.
I deleted and reloaded trunk885 and repeated the above procedure with v100e using my own firmware dump.
The results were identical.
Please can you tell me what I should do next, as I seem to have reached a dead end for the moment!