The environment has changed; the layout is being modified

Hi Friends,

We want to enter plan data for the year 2008.

I`m getting the below mentioned error message when I attempted to "Enter Plan Data" on my Layout:

The environment has changed; the layout is being modified

Incorrect value for charecterstic 0costelemnt, the value was deleted.

Incorrect value for charecterstic 0stkeyfig, the value was deleted

Incorrect value for charecterstic 0zzcr2, the value was deleted.

We did not change any planning level or package... If you want any more information feel free to enquire me...

Please advice me as soon as possible..Appreice you help through points...

Cheers,

PJ