Yes I have admin permissions on both computers. It's definitely not a permissions issue. I had this problem after upgrading to Windows 8.1. It worked fine before. And text and PDF files work fine still, but not ISO and AVI files.
I already updated my network driver (from Realtek) to the latest one, which supports Windows 8 and 8.1. The problem still occurs.
Here's a few things I noticed:
If I put an ISO file on a Windows 7 PC I have, then mount it from my Windows 8.1 PC, then it works.
If I put an ISO file on my Mac...
I have a PC with Windows 8.1 and a Mac with Mavericks. I have a folder on the Mac that is shared with the PC. When I'm on the PC and I try to open a file that is shared by the Mac, such as an ISO file (a disk image), then I get a message saying that I cannot open the file, or the file is in use...