I built a snapshot the other day. That is I created separate copy of all the current source code and built it to give a stable image to some testers. It crashed, just didn’t want to run.

OK, I thought, double check the sources are identical to my development area. Yes & it runs.
OK, I normally build a debug version - the snapshot will be a release build. Build a release build in my development area - it runs.
OK, I build with MSVS work bench but the snapshot is built from the command line so build it from the same command but in my development are. It runs.
Compare the binaries - different sizes, different contents… ?
Clean all objects etc and rebuild everything from scratch in both areas - same results one runs one doesn’t. Do it again in case I got it wrong, check the sources are the same (in case I got it wrong). Do it all over, and again. Phone a friend, search the web, bang head on desk, …

Finally I did what any novice would tell me to do. I switched the PC on and off, then cleaned and re-built the snapshot - it runs.

But why would a build from one command line differ from one in another DOS box (both started from the same Visual Studio command)??? And why didn’t I just try a reset earlier?