Got a problem with GRP order dating can someone please help....?

We are currently experiencing a problem within a BaaN IV environment trying to load demands against a GRP environment passing 24-12-2009.

A demand raised on a Project (Ie Milestone, CCN link & Hardware Demand) have been raised for 18-03-2010 with the top level item containing a 1 day leadtime, 0 safety time and no routing.

PRP has raised a correct MDO, MDD and top level GRP order against the correct date.
When running GRP however, the calculated start date for this item reverts back to 24-12-2009 and proceeds to raise orders for its BoM correctly based on this incorrect date.

We have changed this requirement back and forward in time and all works correctly until we pass the 24-12-2009 date.

We have changed all manner of parameters, project & costing dates, item/group/leadtime settings, raised manual orders directly into GRP, added false routings, etc. to no avail.
We have also cleared down both PRP & GRP system tables to remove any possible corrupting data and still the problem persists.

Any help would be greatly appreciated

Do you get any error messages?

Have you checked if the Company Calendar is set up for future dates?

Could you check if there are any error messages logged in the log.bshell/ log.oracle8 (assuming you are using Oracle).