I am running MT4.2 and also 4.2.1 on another server.. Recently, both started having the same issue and neither blog is related to each other.
When creating a new blog entry, there are the upload image and upload file buttons. The upload image popup normally has options to show a thumbnail of a certain size and check boxes to Display the image in the entry and also to link to a full size pop up..
The box that allows you to input the dimensions disappeared, although the rest of the options remain.. When I have the checkboxes checked to display the image and to link to a popup, then only a link is put in the entry.. the image thumbnail is NOT..
If I uncheck the ‘link to full size version in pop up, Then the image WILL be put inline, however it’s put in full size, not as a thumbnail..
Can anyone help me figure this out? Thanks Brian
Reported on Movable Type 4.2

Sounds like a problem with the ImageMagick installation on the server.
Do you know of 'how' I could check that? I have this on shared hosting and I haven't made any changes myself. It was working and now it's not.
Does mt-check show that ImageMagick is installed?
Thanks. That's it.. I couldn't remember the name of that script, and forgot that it was on the login page.. Image Magick is indeed missing, as well as GD.. I'll have to get it reinstalled.
Hello. My host says that ImageMagick as well as GD are installed, but when I run my mt-check script, it shows:
Your server does not have Image::Magick installed, or Image::Magick requires another module that is not installed. This module is needed if you would like to be able to create thumbnails of uploaded images. Please consult the installation instructions for help in installing Image::Magick.
I get the same message for GD.. I wonder what other module might be required, since it doesn't say? Or if somehow the path to imagemagick might have been lost, and if anyone knows where I can check the path? Is this supposed to be in a .htaccess file, or somewhere else?