Disabling the plugin/hook system via the ACP doesn't resolve the issue. This has happened both on the main board (running 4.1.12 PL1) and the test board (running 4.2.0). However, I could not reproduce the issue here.
Any thoughts?
(EDIT)I reuploaded the 4.1.12 PL1 /clientscript folder to the main board as a test (though no files in said folder have ever been modified) and got the same problem. The Suspect File Versions check doesn't report any issues with vB files. However, the server is running PHP 5.4 (I would hope this isn't the problem, as I can't put it back to 5.3).
(EDIT)Looking at the CKEditor site, it appears that a change in the default encoding of htmlspecialchars() (from ISO-8859-1 to UTF-8) causes the editor to throw a blank box in some instances. Peachy.
I fixed it on my board by the following change to /vb/ckeditor.php
Line 507:
htmlspecialchars($value)
Changed to
htmlspecialchars($value, ENT_COMPAT | ENT_HTML401, "ISO-8859-1")
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