I had the same problem for awhile. It happened when I closed and reopened ePSXe several times due to experimenting with the Graphic Settings. Somehow it fixed itself eventually.
But in the mean time while the bug occurred, instead of mounting the ISO/BIN/IMG files, I just ran them directly through: File, Run ISO. This still worked fine. So use that instead for now.
You can also try restarting your computer if you don't like running the ISOs directly, and see if that fixes it.
But in the mean time while the bug occurred, instead of mounting the ISO/BIN/IMG files, I just ran them directly through: File, Run ISO. This still worked fine. So use that instead for now.
You can also try restarting your computer if you don't like running the ISOs directly, and see if that fixes it.