When you say the "viewing pane", are you referring to the message list, or message pane (message body)?

I am referring to the pane where you double-click the message to view the email itself. All the lists on the left side of T/Bird are visible. Such as inbox, etc.

Okay, that's the message list pane. Try resetting the columns to default.

1. There's a row of column titles (date, subject, size, etc.) along the top. Click on the button at the very right of that row.
2. In the drop-down list, select Reset columns to default.

For more info, see Message List Columns

I did that, nothing changed

Is the account IMAP or POP?

The index file might be corrupt. Thunderbird has a function that will rebuild it.

1. Right-click on the folder, and choose Properties.
2. Click Repair Folder.

Wow, the plot thickens. BTW, thanks for you help.

There are three accounts in this TB agent. Two are imap and one pop. I applied the fix to all three. When the fix is applied the emails show in their proper place I go the the next folder and the same thing occurs. the emails show in their proper place. When I go back to the first fixed folder, they do not appear. I go back to the next repaired folder and they are gone as well. I started over and I can make the emails appear when I repair the folder, both pop and imap. when I try to return to the fixed folder they remain gone. I rebooted TB and no change--no emails. I can see and hear your email pop into the inbox, but it remains invisible to read.... I have another computer running MS10 and the agent is running perfectly in that OS

What antivirus software do you use? Is the Thunderbird profile on your local disk?

( somewhat similar to https://support.mozilla.org/en-US/questions/1137835 ... but for that user it only happens for ONE account)

Fixed one folder, left computer and it continued to download new messages. Went to another inbox and on the return nothing appears. This Linux OS has no antivirus that I can detect.

Which desktop evironment are you using? Are you using mozilla supplied Thunderbird? Or ubuntu distro supplied?

I don't know I think I got it from Ubuntu's apps store.

This version of TB has been working for months

jetcitysteve,

Are you still seeing this problem? Is this a gmail account?

I just mentioned in https://support.mozilla.org/en-US/questions/1137835 that I encountered another gmail user for whom doing repair folder "solved" the problem.