I have a file that isn't very large (>20MB), and it is working and saving just fine. But whenever I add a new levels adjustment layer, it freezes when saving. If I try to save after adding the levels adjustment layer, the "saving" progress bar stops at 0%.
Furthermore, if I try to close Photoshop at this point, it prevents me from saving because it says "Photoshop is saving in the background and will close when finished" but it never saves. I keep having to open the task manager and force quit Photoshop, but the same problem keeps happening even on the recovered files.
Now I'm afraid to add levels adjustments layers, which is a bit problematic.
We're sorry about the trouble with Photoshop while trying to save the files. Would you mind telling us the exact version of Photoshop you're using? You can try disabling the option to Use Graphics Processor from Photoshop by going to Preferences, then Performance. Once done, quit & relaunch Photoshop to check if that helps.