I have one user who's experiencing this error when trying to copy a 42 MB .xls file from one network folder to another network folder (on the same network drive):
An unexpected error is keeping you from copying the file. If you continue to receive this error, you can use the error code to search for help with this problem.
Error: 0x800900006: Invalid Signature.
She's running Windows 7, connecting to Server 2012. Her colleagues have no problem doing the same copy. It may also be worth noting that she has had many more problems than her colleagues combined, and is currently on her third PC, after having been plagued with various problems that could not be solved any other way (mostly issues with network Excel files). She, in turn, plagues me with problems...
If anyone knows how this might be solved, I would greatly appreciate it.