Filemaker 9 Bug

Has anybody experienced a failure within a new calculation of the "Evaluate this calculation from the context of.... " list to update with all appropriate relationships in the relationship graph. My file which started life in FM5 lost its reference to the main table recently, necessitating all new calculations to be copied from a previous calculation, which still had the full list, and then amended.

I have partially overcome this problem by deleting the two relationships that remained in the list. Somehow this forced the main table to reappear in any new calculations and a couple of others popped up as well. However, I am still missing about 20 that have been created over time.

I would rather not delete these 20 as well and reinstate them because this appears to corrupt relationships / lookups in other files which use this file, not necessarily these relationships. There must be an underlying table that is being referenced and has become corrupted. Any ideas how I might force it to behave, please?