"Edit Definition" option not available for parts of assembly

[Geneg]

Using Creo 8.0 and WC 12.

I have an assy that was created a while ago.

Some parts and sub assys are editable, but some are not.

Any suggestions on the subject?

Thanks

 

[Geneg]

I brought assy out of WC. I deleted questionable components, assembled them back in different order...same result...NOT editable. Lost, never saw it in my 25 years of ProE/Creo modeling.