Hi,
The table header is corrupted, i.e. the file size in the header does not equal the actual table size. i.e. probably has record fragment on end of file. Also the prg must use transaction tracking, as any appends from the prg will not be saved - Documented bug.

Quickest way to fix - Append blank record to end of file on site, use XRAY, can download from download section. Delete appended record, then reindex and pack. This overwrites the record fragment, then all is happy.

Answer to your next question is, The reason why it worked when u appended record to the file, is because u didn't have transaction tracking on.

Hope this helps.