Enter layout mode. Change the optimization back to Image or add a new copy of the field with image optimization specified. Return to Browse mode. Click the field while in browse mode and press the delete key.
In a script:
Set Field [YourTable::YourContainerField ; "" ]
Clear [YourTable::YourContainerFIeld ]
Clear requires that the field be present and accessible on the current layout. Set Field does not.
More simple:select the container field; Edit/Clear...
Thanks PhilModJunk--Sorry I didn't acknowledge your help. It worked--maybe some glitch had been introduced during construction, but why it came on suddenly I'll never know.
Jordi Badia: Had the original problem not gone away, your solution would not have worked; however, now yours does and I'm a happy camper all-around!