When using javascript to assign a value to a textarea, the textarea's value will instead be reverted to it's default if the textarea is hidden (e.g., inside a div with "display: none", etc.). I will attach an HTML file that includes a form with Javascript for reproducing the bug.
Created attachment 12612 [details] HTML Form, Javascript, and instructions for reproducing this bug
This seems to be fixed on ToT.
Jamis, thanks for taking the time to file this bug! This works for me testing with a locally-built debug build of WebKit r19028 with Safari 2.0.4 (419.3) on Mac OS X 10.4.8 (8N1037). Therefore closing as RESOLVED/FIXED. Please see Bug 12199 Comment #3 for speculation on when a fixed version of WebKit may be available. You may test other bugs using a nightly build from http://nightly.webkit.org/.