I've been using Blender for over a year now, and this is the first time I have had this problem. I am editing a small 2000 frame video, but ever since I saved it the preview will not show images or play audio clips. Rendering it still upholds the transparent (checkered) image. But, there is one thing. A singular picture shows around the 1500 mark and a singular video clip shows directly after. After this video clip the preview goes back to transparent. This shows that there is not a problem with preview, but with the settings.
What could have caused this? It's a genuine emergency that I have to resolve ASAP.