.png file not showing up on windows VM

Hello,

I have users who are having issues seeing .png files when using a windows VM. This is a windows environment. The business partner is using a Mac pro and creates the .png file in creative suite and saves the file to a windows 2008 server. When they try to insert the file into a powerpoint on their Windows 7 VM, they cannot find the file. It shows up about 10-15 mins later. But they can access it from the Mac right away. We are running Extremez IP on the server. Is this a known issue with this OS/macs in windows environment/extremez IP?