"The environment has changed; the layout can no longer be executed"

Hi guys,

I have revceived a planning area complete with planning level, package and layout. When I want to enter plan data, I get the following error message.

"The environment has changed; the layout can no longer be executed"

In order to try to re-generate, I opened the layout and planning area, level, package in change mode, then saved but it was no help.

Any ideas

Thanks,

Rod