Since Order Entry affects the Accounts Receivable files as well as the Order Entry files, when a problem occurs you may either restrict your remedy to the Order Entry files or you must include the Accounts Receivable files also - depending on what you were doing.  It should be reasonably obvious that only invoicing and recording a deposit from a customer affect the AR files. Otherwise, the only affected files are OE. Regardless, all AR and OE files are opened when you use the Order Entry module; even though an update may not occur, a search certainly will.
Problems that require reindexing files lock up your computer. That is
so you will not further corrupt the data files by continuing to process. Yes,
we are aware that the error message says "then press ENTER" and we are also
aware that it fails. All you can do is reboot your computer.
Here is a list of errors that usually require reindex:
Since you're seeing this, you have access to the latest software updates. Except
when you fall into one of the following categories, you should start your
troubleshooting by FTP'ing the "OE and PO" update. Install it per the
instructions on that page.
If you run OECLEAN, always DISPLAY the output. If you try to print it, it may send your printer into "Never Never Land" but if you display, your monitor will gracefully handle (almost) anything sent to it. When the "OECLEAN DELETION LIST" displays, just <ESC>ape and then Cancel. Now you will see a listing that says how many of which records OECLEAN wants to delete. <ENTER> will delete the problematic records. Except in unusual circumstances, the records that OECLEAN wants to remove are junk, so deleting them will not affect your data negatively. One "unusual circumstance" would be a corrupt Order Header file.  That can cause records to be candidates for deletion when they should not be deleted.
So the word to the wise is, "reindex the OE files if you encounter an unusually large number of records to delete" when you run OECLEAN. And always have a backup.