>quickscanning the code turned up no gotchas for me - as you isolated a stream and CRC that, first impulse is to suspect versioning. As this sounds stupid as well, setting up VMs with Dotnet 4.5 and another, older one and to compare CRC results done from "local VM system disc" and shared drives would be next step for me. PITA...

Yes, that is pretty much what I had in my agenda for tomorrow.

Quick correction however, what I meant was that the file size on disk differs in the new environment and that doing a CRC32 on a file size which is different from one environment to another, for the same file, will thus create a different CRC32.

So, this leads to think that the problem is in fact the storage mechanism on the NAS. I will verify the file size recognized from Windows on a file stored on the C: drive and the same file stored on the NAS.