I use thunderbird to read the newsgroup, current version is 1.0. When the news has attachment and the name of attachment is longer than the width of attachment window, the vertical scroll bar of the message window is disappeared. I need to click on other news in order to make the attachment window disappear and the scroll bar of message window restore to original look. Remark: the message window is the window that has the clickable column for message sorting.
What you refer to as "message window" is called "thread pane". Note that the right edge of the message pane is also truncated, possibly hiding a scrollbar for that pane as well. This is the same basic problem as Seamonkey bug 247833 / bug 118513. xref TB bug 223340, bug 242531.
Looks like a duplicate of bug 269246 (or vice versa).
Agree about the dupe. *** This bug has been marked as a duplicate of 269246 ***