Well, if all the possibilties in my original post on top of this thread fail, the only way is to reinstall MacOS completely from scratch.
- Make a backup of all your data or your complete boot drive, just in case (use Time Machine or Carbon Copy Cloner, e.g.).
- boot into your recovery partition (press Command-R at the startup chime a few seconds)
- reinstall MacOS (you should not loose any of your data, but the backup from step one makes you feel better ;-)
- after reboot, apply any OS updates via App Store, if any.
This helped in my case.
My guess is that one of the recent Java Updates of Apple damaged a system file (this is why sometimes resetting Java seems to help). This damaged (or missing) file is now overwritten by a new one - and all is up and working again.
I hope, that helps you too.
I found something, which might help as well. Could explain, why resetting Java sometimes halps and sometimes does not:
Mail is a sandboxed application, AFAIK.
Maybe following the hints at the end of this article helps. If so, please let me know. I cannot check this anymore.
Just wanted to say that I got the same prolem too.
I bought a new SSD and installed a whole new OS 10.6.8.
This problem was in previous system on the previous HD, and it exists again under my new system.
This problem happens to me too when I use Flickr uploadr, When I drag photos over there, it says the same like when I add photos to a mail message.
I didn't understand which solution worked.
All the best,
Identical problem - running System 10.7.5 - "missing plug-in" showing in Apple Mail, where a jpeg image or photo is expected. Problem appeared recently, don't know why.
Came here to find solutions - found Graham's - and hopefully improved on it:
This works for my case:
Did not need to close (quit) the Mail program and relaunch.
1. Just a simple click to open another message. Then,
2. Click back to problem message. jpeg image/photo appears as expected, without "missing plug-in" message.
(in other words, close the problem message and re-open it.) no need to quit entire Mail app.
did not need to mess with Safe Boot, System re-install, Java Preferences, Time Machine, Carbon Copy cloning, switching out hard drives, messing with System files, etc., etc.
again, works for my case - hopefully works for a few others, too. yes, very irritating.
very grateful for postings here.
My strange story: I'm on 10.6.8 for a while on Mac Pro. I never had any problem with Mail. (I always could see attachemnts displayed, either JPEG, PDF or any..)
Today I sent an email, and saw in my sent emails folder that "missing plug-in" .. and after a few clicks ran onto this thread here.
I just wanted to say that this is a bug in OSX, and a simple way to solve it: just search into your sent emails any email with an attachment that is an image; it will be displayed !! Then go back to the "missing plug-in" bug and you will see the bug is gone.
I was searching for something else and found this. Just so you know - this is a java error. Open up Java preferences and clear the cache. Should fix your problem. Doesn't fix it permanently but it's an easy fix and you can keep doing it every time it happens. The newer versions of OSX don't have this problem anymore. I'm on 10.9 now and haven't had this issue in months.