Lost mail, locked settings?

Thunderbird Portable 2.0.0.14 on PNY 1GB usb stick.
ONE of my four popped Gmail accounts has lost messages and will not allow settings changes.

I have deleted msf files tried compacting etc.
Appears as two unread three total but nothing shows in message list pane or preview pane.

Unusual behavior:

1) Additional property tabs
Right click - Inbox of any other gmail account shows properties shows General Information and Retention Policy tabs. Account in trouble ALSO has Offline Sharing and Quota tabs.

2) Incorrect setting cannot be changed
All other accounts use Retention policy setting of "Don't delete any messages"
Bad account has Use Server dafaults and Always delete read messages set on.
I tried correcting the settings, clicked ok. Window will not close until I hit Cancel.

Your thoughts?

WP