SAP Note 22637 - IP10 : Error CO901 when calling maintenance plan

Symptom:

When calling the maintenance plan via transaction IP10 or via the monitoring tool IP30, message CO901 is displayed: 'Program error (contact your system administrator'.

Cause and prerequisites

A start date in the past was calculated. A regular maintenance order is now to be created at this date. Plans allocated to the maintenance item are either not available or not yet valid at this time.
Please note that the start date is calculated from the calculated planned date minus the preliminary float lead times.
In strategy-controlled maintenance plans, these floats are stored in strategy table T351. In plans without strategies (multiple counter), these floats are linked to the maintenance plan header under the scheduling parameters.

Solution

1. Allocate valid plans to the maintenance items
or

2. make the scheduling at times where the plans are valid (calculated planned date is greater than or equal to the valid-from date in the routing header).