Here's what I would try. Open Write. Right click in space on Toolbar. Click Customize. Make sure to drag your Contacts button onto the Toolbar. Click Done. Now click on that Contact button and the Address book should appear.

It usually is there with every new message, unless you un-check that button and close the message. If that happens just click on it again.

Does that work?

Open a Write window and press F9.

Thanks for the replies. I tried both suggestions with no luck. I have spent some time on this problem and I think as a last resort I may have to delete the Thunderbird program and reload it from start.

If you go to View-Layout is Contact Sidebar checked? Do this in a Write window. If it is checked, move your mouse to the left side of the window. Watch for it to change to a double headed arrow. When it does left click, hold and drag to the right. The Write window needs to be maximized for this.

Try creating a New Profile and checking to see if it works in the new profile. Then maybe you can figure out what's different.

Search support for Using Profiles  or something like that.

There is no Menu or Mail toolbar in my Write window.

Try this. Open your Write window. Go to your Title Bar Menu up at the very top. To the right of the Apple Logo. Go to the 4th one over -- View. Click on View, then click on Toolbars - make sure all three are checked one by one. You can always uncheck the ones you don't want. Then also Go to View and check the Contacts Sidebar.

post back....

Looks like you are using Windows. Pressing the alt key or F10 reveals the Menu Bar. Select View-Toolbars and turn them back on.