Try restarting your computer.
Also try a Ctrl-Q rebuild.
Do you have Microsoft Updates set to automatically apply updates? Did you video card driver get updated over the weekend? What other things might your IT department have done over the last few days?
Microsoft is set to auto update.
I check video card driver and it is the same recommended driver from Solidworks.
There have not been any changes from IT dept.
One thing I noticed, if I save a part to my desktop, that part will show when I hit "R" key, but all the parts saved to the network still do not show.
Check the File Locations in the Options hasn't been altered.
Could also be a network problem.
The "Loading..." text is shown for any non-local file as we are retrieving the image. Since this action may be slower then retrieving images from local files, we create a separate thread to grab the images and we display the "Loading..." text while the thread is processing the network request.
I'd expect you are having network performance issues, or perhaps the particular server is down, or a mapped network drive or shortcut is no longer valid.