>The files are still all in the same place on the network file server. I'm beginning to think it's purely a network issue sometimes it opens fast (2-3) seconds and sometimes slow.

I would say that is the problem. If you’re on a segmented network you may have been moved to a different segment. If this is the case then you may be contending with increased traffic or worse, having to go through a router (arrgh!) to get to your default file server. You might find it less frustrating to move your work files local and use the server for backup.