Help! "File attachments" error and hanging "gray box"

This worked until recently, but now when I try to attach an image in "File attachments" within content, I get the following kind of error in a popup box. When I submit the content, the image is indeed there, but it's actually there in duplicate.

When I delete one and resubmit, everything's fine, but this shouldn't be happening and I don't know why it is. When I first submit the image, I get the error message below and the image doesn't show it's there until I do what I mention above. Can anyone see what's happening here and how I can fix it?

An error occurred:

{ "status": true, "data": "\x3ctable\x3e\n \x3cthead\x3e\x3ctr\x3e\x3cth\x3eDelete\x3c/th\x3e\x3cth\x3eList\x3c/th\x3e\x3cth\x3eDescription\x3c/th\x3e\x3cth\x3eSize\x3c/th\x3e \x3c/tr\x3e\x3c/thead\x3e\n\x3ctbody\x3e\n \x3ctr class=\"odd\"\x3e\x3ctd\x3e\x3cdiv class=\"form-item\"\x3e\n \x3cinput type=\"checkbox\" name=\"files[upload_0][remove]\" id=\"edit-files-upload-0-remove\" value=\"1\" class=\"form-checkbox\" /\x3e\n\x3c/div\x3e\n\x3c/td\x3e\x3ctd\x3e\x3cdiv class=\"form-item\"\x3e\n \x3cinput type=\"checkbox\" name=\"files[upload_0][list]\" id=\"edit-files-upload-0-list\" value=\"1\" class=\"form-checkbox\" /\x3e\n\x3c/div\x3e\n\x3c/td\x3e\x3ctd\x3e\x3cdiv class=\"form-item\"\x3e\n \x3cinput type=\"text\" maxlength=\"256\" name=\"files[upload_0][description]\" id=\"edit-files-upload-0-description\" size=\"60\" value=\"jennifersbody_meganfox.jpg\" class=\"form-text\" /\x3e\n \x3cdiv class=\"description\"\x3e\x3csmall\x3ehttp://www.hollywoodchicago.com/sites/default/files/jennifersbody_meganfox.jpg\x3c/small\x3e\x3c/div\x3e\n\x3c/div\x3e\n\x3c/td\x3e\x3ctd\x3e27.53 KB\x3c/td\x3e \x3c/tr\x3e\n\x3c/tbody\x3e\x3c/table\x3e\n\x3cdiv id=\"attach-hide\"\x3e\x3cdiv class=\"form-item\"\x3e\n \x3clabel for=\"edit-upload\"\x3eAttach new file: \x3c/label\x3e\n \x3cinput type=\"file\" name=\"files[upload]\" class=\"form-file\" id=\"edit-upload\" size=\"40\" /\x3e\n\n\x3c/div\x3e\n\x3cinput type=\"submit\" name=\"attach\" id=\"attach-button\" value=\"Attach\" class=\"form-submit\" /\x3e\n\x3c/div\x3e\x3cinput type=\"hidden\" name=\"attach-url\" id=\"edit-attach-url\" value=\"http://www.hollywoodchicago.com/upload/js\" class=\"upload\" /\x3e\n\x3cinput type=\"hidden\" name=\"vid\" id=\"edit-vid\" value=\"\" /\x3e\n" }