It would be extremly helpful if you provide VFP version you're using. My guess, is it's VFP9. The expression of the index key you posted is not good for index because key size and value depends on SET DATE setting. See Considerations for Creating Index Expressions in VFP9 help for details.
The corerct expression is

DTOC(poDate,1) + poNum

>
>I have a problem that ONLY emerges when I move a DB to the Novell network. It does not occur when testing on a local where the DB is installed on the local. It does occur when the DB is installed on a network drive. The offending index is:
>

> DTOC(poDate)+ poNum.
>

>It blows up on an "append blank" when an index has to be regenerated. I have no problem re-indexing the table from the command window or validating the database. The error generated is 2199 which occurs when index key truncation is about to occur resulting from a key that contains an expression involving a Memo field, whose length is not fixed. This error came out of nowhere, however, I had added some complex sql to the project.