My problem is that the .Net IDE regularly reports "phantom" compilation
errors. Just like "real" errors, I see them in the task window, and the lines
of code are highlighted in the code window, and the solution will not build.
But I know they are "phantoms" because the lines of code have not changed in
many months and if I either rebuild my solution (i.e. rebuild not build) or I
edit any line in each of the code files that is reporting an error (i.e. make
any change and then put the change back again), then the errors simply
disappear.

To begin with the problem only appeared in certain files and only
infrequently. But now they appear in quite a few files (20 or so) and
regularly (perhaps 10 times a day). Rebuilding the solution takes 20 seconds
or so and is therefore a real nuisance. Can anyone give me a hint at the
cause. I've rebuilt the solution from scratch (i.e. deleted all the project
files, created new project files, recreated all the references, etc) but this
made no difference!