I ran my invoice database through a trial run.  Currently, I am use Sesame Personal 2.6.3 .

It is installed on a local drive, but the computer is on a network.  When I try deleting or mass deleting, I cannot do it.

I get a message : This entry cannot be deleted.  It is likely that another user is viewing this entry.

The problem is there are no one else using the program or viewing the records.

There are no security settings on this database as it is still in test mode.

No, that was not the problem.
I did figure it out though.
As I was trying to add more features to the program, this glitch started.  So I try previous versions to see if they had the same problem, but I could delete and mass delete.
The problem was my invoice program had a sub form for items and a second sub form for calculations.  Sesame does not allow a second sub form.

I was able to make it work by having the second sub form items added to the main form with the sub form over it.  The user can switch the visibility of the sub form off to see the calculation option.

All's good, so far.

I was not accessing the same set of records, unless it thinks I was, but the second sub form was unnecessary.

The first sub form was for items.
The second sub form was for cash payment in separate denominations. 

My intent was to switch between sub forms base on the where the user was in the invoice.  Instead of having a cash sub form, I just put the fields in the main form and switch on the visibility when needed.