Two things I note with your code.

You shouldn't 'set order to nwork' and then 'delete for nwork=' this could cause problems if the index excludes deleted records.
After you pack, 'Use In works' before closing database.

I don't think these cause your problem but may be worth a try.

>You excuse, my English is bad. I have a table: works.dbf index for work number and that it generates the file: works.cdx.
>When one makes an invoice i make the following:
>use works exclusive
>set order to nwork
>delete for nwork=thisform.text1.value
>pack
>close databases
>
>The index is sometimes corrupted and when looking in the directory of server the size of file works.cdx is 0. Where this the problem?, Can it have an error in the communication client-server?
>The configuration is:
>Server: Windows NT, VFP6, application and dbf, cdx, forms, reports...
>Client: Windows 98 and Vfp6r.dll
>Thank you