This error can be caused by an employee data item that does not have an internal system number assigned.  

Run a summary list for all of the Employee Data items.  (Report Manager, Payroll/Personnel, Master Record Lists, Employee Data Items List)
Look in the column labeled "Nbr" to see if there are any blanks. Remove the employee data item.  This can be done through Define Employee Data items if it is not on any employee records. 
If the employee data item cannot be removed because it is attached to an employee, call Fundware Support for further diagnostic steps.

If you do not have any blank items, do the following:

Run Program: PYL901 with no Switches: and no Parameters: 

1. Make sure all users are logged out of payroll.
2. We recommend making a backup before running any utilities on your data files. 
3.  Select File -> Open FundWare.
4.  Verify that 00 - System Administration appears in the drop down box, click OK.
5.  Select System Administration -> System Utilities.
6.  Enter the following in the Execute Program portion of the screen:       
Program Name                   PYL901        
Switches                            <blank>       
Parameters                        <blank>       
Business Date                    Use today's date       
Division                  Select the appropriate division.       
Click Run.
7.  Say, yes, you are sure you want to do this.
8.  Say, yes, you want to file a report. 
This will create report PYL901.L##  in the Fundware\Data folder.  This will report any duplicate data item numbers in the ##CID file.   Running PYL901 with switch 1, no parameters, will delete those data items that show up on the PYL901 report.  If you delete all PYL901 reports from the print manager, then run PYL901 , with no switches and no parameters again, the report should be blank. 
If neither of the above solutions fix this error, try reorging (BB710582) the division ##py* and ##ci* files.