I've had this twice. One time was fixed by restoring the Providex.xxx files, the second was fixed by this SYZCON process:
1. From the Sage 100 ERP Desktop, click File menu, select Run
2. For the Program field enter the following command and press the Enter key: SYZCON
3. Click OK
4. At the prompt type the following: PRINT %SYS_SS'CreateTable(""table"",""COMPANY:xxx"")
1. Note: Replace table with the name of the table the lookup is using. Replace xxx with the company code affected
5. Press the Enter key
6. Repeat this process for each table and company code where this issue appears