New product showing other products' images

When adding new product images via Magento admin panel, clicking “Browse Files” and then clicking “Upload Files” (do not save), the images showing are other products’ images. And then clicking “Save and Continue Edit”, the images just uploaded showed. Most of our products' images are named “1, 2, 3,4, 5…”.
We found magmi.php virus after this problem happened. We removed the virus, but this problem was not solved.